Refresh 9.0 branch README (#2848)

Author: JoshMock

README.md

@@ -2,7 +2,7 @@
 
 # Elasticsearch Node.js client
 
-[![js-standard-style](https://img.shields.io/badge/code%20style-standard-brightgreen.svg?style=flat)](http://standardjs.com/)  [![Build Status](https://badge.buildkite.com/15e4246eb268ea78f6e10aa90bce38c1abb0a4489e79f5a0ac.svg)](https://buildkite.com/elastic/elasticsearch-javascript-client-integration-tests/builds?branch=main)  [![Node CI](https://github.com/elastic/elasticsearch-js/actions/workflows/nodejs.yml/badge.svg)](https://github.com/elastic/elasticsearch-js/actions/workflows/nodejs.yml)  [![codecov](https://codecov.io/gh/elastic/elasticsearch-js/branch/master/graph/badge.svg)](https://codecov.io/gh/elastic/elasticsearch-js)  [![NPM downloads](https://img.shields.io/npm/dm/@elastic/elasticsearch.svg?style=flat)](https://www.npmjs.com/package/@elastic/elasticsearch)
+[![js-standard-style](https://img.shields.io/badge/code%20style-standard-brightgreen.svg?style=flat)](http://standardjs.com/) [![Build Status](https://badge.buildkite.com/15e4246eb268ea78f6e10aa90bce38c1abb0a4489e79f5a0ac.svg)](https://buildkite.com/elastic/elasticsearch-javascript-client-integration-tests/builds?branch=main) [![Node CI](https://github.com/elastic/elasticsearch-js/actions/workflows/nodejs.yml/badge.svg)](https://github.com/elastic/elasticsearch-js/actions/workflows/nodejs.yml) [![codecov](https://codecov.io/gh/elastic/elasticsearch-js/branch/master/graph/badge.svg)](https://codecov.io/gh/elastic/elasticsearch-js) [![NPM downloads](https://img.shields.io/npm/dm/@elastic/elasticsearch.svg?style=flat)](https://www.npmjs.com/package/@elastic/elasticsearch)
 
 **[Download the latest version of Elasticsearch](https://www.elastic.co/downloads/elasticsearch)**
 or
@@ -34,25 +34,26 @@ the new features of the 8.13 version of Elasticsearch, the 8.13 client version
 is required for that. Elasticsearch language clients are only backwards
 compatible with default distributions and without guarantees made.
 
-| Elasticsearch Version | Elasticsearch-JS Branch  | Supported |
-| --------------------- | ------------------------ | --------- |
-| main                  | main                     |           |
-| 8.x                   | 8.x                      | 8.x       |
-| 7.x                   | 7.x                      | 7.17      |
+| Elasticsearch Version | Elasticsearch-JS Branch |
+| --------------------- | ----------------------- |
+| main                  | main                    |
+| 9.x                   | 9.x                     |
+| 8.x                   | 8.x                     |
+| 7.x                   | 7.x                     |
 
 ## Usage
 
-* [Creating an index](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/getting-started-js.html#_creating_an_index)
-* [Indexing a document](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/getting-started-js.html#_indexing_documents)
-* [Getting documents](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/getting-started-js.html#_getting_documents)
-* [Searching documents](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/getting-started-js.html#_searching_documents)
-* [Updating documents](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/getting-started-js.html#_updating_documents)
-* [Deleting documents](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/getting-started-js.html#_deleting_documents)
-* [Deleting an index](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/getting-started-js.html#_deleting_an_index)
+- [Creating an index](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/getting-started-js.html#_creating_an_index)
+- [Indexing a document](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/getting-started-js.html#_indexing_documents)
+- [Getting documents](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/getting-started-js.html#_getting_documents)
+- [Searching documents](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/getting-started-js.html#_searching_documents)
+- [Updating documents](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/getting-started-js.html#_updating_documents)
+- [Deleting documents](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/getting-started-js.html#_deleting_documents)
+- [Deleting an index](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/getting-started-js.html#_deleting_an_index)
 
 ### Node.js support
 
-NOTE: The minimum supported version of Node.js is `v18`.
+NOTE: The minimum supported version of Node.js is `v20`.
 
 The client versioning follows the Elastic Stack versioning, this means that
 major, minor, and patch releases are done following a precise schedule that
@@ -65,58 +66,43 @@ to support that version for at least another minor release. If you are using the
 with a version of Node.js that will be unsupported soon, you will see a warning
 in your logs (the client will start logging the warning with two minors in advance).
 
-Unless you are **always** using a supported version of Node.js, 
+Unless you are **always** using a supported version of Node.js,
 we recommend defining the client dependency in your
 `package.json` with the `~` instead of `^`. In this way, you will lock the
 dependency on the minor release and not the major. (for example, `~7.10.0` instead
 of `^7.10.0`).
 
-| Node.js Version | Node.js EOL date | End of support         |
-| --------------- |------------------| ---------------------- |
-| `8.x`           | `December 2019`  | `7.11` (early 2021)    |
-| `10.x`          | `April 2021`     | `7.12` (mid 2021)      |
-| `12.x`          | `April 2022`     | `8.2` (early 2022)     |
-| `14.x`          | `April 2023`     | `8.8` (early 2023)     |
-| `16.x`          | `September 2023` | `8.11` (late 2023)     |
-
-### Compatibility
-
-Language clients are forward compatible; meaning that clients support communicating with greater or equal minor versions of Elasticsearch.
-Elasticsearch language clients are only backwards compatible with default distributions and without guarantees made.
-
-| Elasticsearch Version | Client Version |
-| --------------------- |----------------|
-| `8.x`                 | `8.x`          |
-| `7.x`                 | `7.x`          |
-| `6.x`                 | `6.x`          |
-| `5.x`                 | `5.x`          |
-
-To install a specific major of the client, run the following command:
-```
-npm install @elastic/elasticsearch@<major>
-```
+| Node.js Version | Node.js EOL date | End of support      |
+| --------------- | ---------------- | ------------------- |
+| `8.x`           | `December 2019`  | `7.11` (early 2021) |
+| `10.x`          | `April 2021`     | `7.12` (mid 2021)   |
+| `12.x`          | `April 2022`     | `8.2` (early 2022)  |
+| `14.x`          | `April 2023`     | `8.8` (early 2023)  |
+| `16.x`          | `September 2023` | `8.11` (late 2023)  |
+| `18.x`          | `April 2025`     | `9.1` (mid 2025)    |
 
 #### Browser
 
 > [!WARNING]
 > There is no official support for the browser environment. It exposes your Elasticsearch instance to everyone, which could lead to security issues.
-We recommend that you write a lightweight proxy that uses this client instead, you can see a proxy example [here](./docs/examples/proxy).
+> We recommend that you write a lightweight proxy that uses this client instead, you can see a proxy example [here](./docs/examples/proxy).
 
 ## Documentation
 
-* [Introduction](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/introduction.html)
-* [Usage](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/client-connecting.html#client-usage)
-* [Client configuration](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/client-configuration.html)
-* [API reference](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/api-reference.html)
-* [Authentication](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/client-connecting.html#authentication)
-* [Observability](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/observability.html)
-* [Creating a child client](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/child.html)
-* [Client helpers](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/client-helpers.html)
-* [Typescript support](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/typescript.html)
-* [Testing](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/client-testing.html)
-* [Examples](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/examples.html)
+- [Introduction](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/introduction.html)
+- [Usage](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/client-connecting.html#client-usage)
+- [Client configuration](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/client-configuration.html)
+- [API reference](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/api-reference.html)
+- [Authentication](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/client-connecting.html#authentication)
+- [Observability](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/observability.html)
+- [Creating a child client](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/child.html)
+- [Client helpers](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/client-helpers.html)
+- [Typescript support](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/typescript.html)
+- [Testing](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/client-testing.html)
+- [Examples](https://www.elastic.co/guide/en/elasticsearch/client/javascript-api/current/examples.html)
 
 ## Install multiple versions
+
 If you are using multiple versions of Elasticsearch, you need to use multiple versions of the client. In the past, install multiple versions of the same package was not possible, but with `npm v6.9`, you can do that via aliasing.
 
 The command you must run to install different version of the client is:
@@ -161,7 +147,7 @@ client7.info().then(console.log, console.log)
 ```
 
 Finally, if you want to install the client for the next version of Elasticsearch
-*(the one that lives in Elasticsearch’s main branch)*, you can use the following
+_(the one that lives in Elasticsearch’s main branch)_, you can use the following
 command:
 
 ```sh