Revamp overview page of docs

Author: triblondon

documentation/docs/index.mdx

@@ -8,43 +8,41 @@ pagination_prev: null
 
 import {Fiddle} from '@site/src/components/fiddle';
 
-# Getting started
+# JavaScript for Compute@Edge
 
-First, make sure to have [Fastly's CLI](https://developer.fastly.com/learning/tools/cli/) installed:
+This site is the full SDK reference for [@fastly/js-compute](https://www.npmjs.com/package/@fastly/js-compute), the module that provides the interface between your JavaScript code and the [Fastly](https://www.fastly.com) Compute@Edge platform.
 
-The Fastly CLI is available for multiple operating systems.
+If you haven't used Compute@Edge before, start by [setting up your first Compute@Edge program](https://developer.fastly.com/learning/compute/) over on **developer.fastly.com** so that you have a working development environment.
 
-- **MacOS**: Install from Homebrew:
+To learn more about the fundamentals of using JavaScript with Compute@Edge, see our [using JavaScript](https://developer.fastly.com/learning/compute/javascript/) guide.
 
-    ```
-    brew install fastly/tap/fastly
-    ```
+## Understanding the JavaScript SDK
 
-- **Windows**: [Visit the GitHub repository](https://github.com/fastly/cli/releases/latest) to download the prebuilt binary for your architecture.
-- **Linux**: Packages are available for many distributions, along with prebuilt binaries. [Visit the GitHub repository](https://github.com/fastly/cli/releases/latest) to download the package for your distribution.
+Incoming HTTP requests to domains that are attached to your Fastly service will start an instance of your application and invoke a `fetch` event, which can be bound using the `addEventListener` function:
 
-## Initialise a new project
+```js
+addEventListener("fetch", event => event.respondWith(handleRequest(event)) );
 
-Create a new Fastly Compute@Edge JavaScript project:
+async function handleRequest(event) {
+  const req = event.request;
 
-```shell
-fastly compute init --language javascript --from https://github.com/fastly/compute-starter-kit-javascript-empty
+  return fetch(req, {
+    backend: "example_backend"
+  });
+}
 ```
 
-Install the dependencies:
+Fastly specific features are available as named imports from `fastly:` prefixed modules, all of which are documented in this site.  For example, the [env](https://js-compute-reference-docs.edgecompute.app/docs/fastly:env/env) function provides access to [environment variables](https://developer.fastly.com/reference/compute/ecp-env/) and can be imported into your application like this:
 
-```
-npm install
+```js
+import { env } from "fastly:env"
 ```
 
-## Try it out locally
+JavaScript code compiled for Compute@Edge has access to a global environment with most of the globals you would expect in an ECMAScript runtime, like [`Date`](https://js-compute-reference-docs.edgecompute.app/docs/globals/Date/) and [`console`](https://js-compute-reference-docs.edgecompute.app/docs/globals/console/log).
 
+## Trying things out
 
-```shell
-fastly compute serve --watch
-```
-
-Your application should now be running on [http://localhost:7676](http://localhost:7676)
+[Fastly fiddle](https://fiddle.fastly.dev) is an online web-based playground where you can run Fastly code.  You'll see fiddles included in many pages of our [developer hub](https://developer.fastly.com) and this SDK reference. These interactive examples can be executed right on the page by clicking the **RUN** tab:
 
 <Fiddle config={{
   "type": "javascript",
@@ -96,3 +94,5 @@ addEventListener("fetch", event => {
 ```
 
 </Fiddle>
+
+Check out [`fiddle.fastly.dev`](https://fiddle.fastly.dev] to create your own.