docs: add Readme for sdm commands

airbyte_cdk/cli/source_declarative_manifest/README.md

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+# Source Declarative Manifest CLI
+
+The source-declarative-manifest CLI is included in the airbyte-cdk package.
+This CLI enables connector interfaces to be run locally on manifest-only connectors,
+much like we already do with Python connectors.
+
+## Installation
+
+The airbyte-cdk library can be installed globally using pipx:
+
+```bash
+pipx install airbyte-cdk
+```
+
+If you are using a cloned airbyte-python-cdk repo locally,
+you can also create a virtual environment to enable the CLI.
+From the root directory of airbyte-python-cdk:
+
+```bash
+python -m venv .venv
+source .venv/bin/activate
+pip install -e .
+```
+
+## Usage
+
+### Options
+
+--help: displays the list of available commands
+
+### Commands
+
+- spec: Outputs the JSON configuration specification. NOTE: This currently just outputs the base source-declarative-manifest spec
+- check: Runs a connection_check to verify a connection can be made with the passed config
+- discover: Outputs a catalog describing the source's schema
+- read: Reads the source using the passed config and catalog, and outputs messages to STDOUT
+
+### Command options
+
+- --config: The relative path to the config to inject into SDM.
+- --catalog: The relative path to the configured catalog.
+- --state: The relative path to the state object to pass. Only used when running an incremental read.
+- --manifest-path: The relative path to the local YAML manifest to inject into SDM.
+- --components-path: The relative path to the custom components to mount, if they exist.
+
+| Option              | spec | check    | discover | read     |
+| ------------------- | ---- | -------- | -------- | -------- |
+| `--config`          | ❌   | required | required | required |
+| `--catalog`         | ❌   | ❌       | required | required |
+| `--state`           | ❌   | ❌       | ❌       | optional |
+| `--manifest-path`   | ❌   | required | required | required |
+| `--components-path` | ❌   | optional | optional | optional |
+
+### Examples
+
+Here are some basic examples of how to run source-declarative-manifest commands locally.
+Note that the paths are relative. These example assume the user is currently at the root level of a connector dir:
+
+```bash
+source-declarative-manifest check --config secrets/config.json --manifest-path manifest.yaml
+```
+
+```bash
+source-declarative-manifest read --config secrets/config.json --catalog integration_tests/configured_catalog.json --manifest-path manifest.yaml --components-path components.py
+```