Updates to extension documentation (Azure#210)

* doc for vendored_sdks folder

* add README to point at extension docs in azure-cli folder

* forgot to add docs readme

README.md

@@ -28,6 +28,7 @@ Add your extension to the index to make it available in these CLI commands:
 - Extension source code goes into the `src` directory.
 - You can place your source code in this repository by creating a PR.
 - Once CI is green and it has been approved, the PR can be merged.
+- SDKs generated from [AutoRest](https://github.com/Azure/autorest) often do not pass CI static-checking. If they are vendored inside the extension, exclude them from static checking by placing them in the folder: `src/<extension root>/azext_*/vendored_sdks`.
 - Ensure that you include an appropriate owner for your extension in `.github/CODEOWNERS`.
 - Your extension artifact (i.e. `.whl`) will not live in this repository. You can publish your extension to PyPI or somewhere else such as Azure Storage.
 - If you want your extension to appear in the index.json, modify the index.

docs/README.md

@@ -0,0 +1,21 @@
+Azure CLI Extension Documention
+=======================
+Information
+------------
+
+Take a look at: [Azure CLI Extensions](https://github.com/Azure/azure-cli/tree/dev/doc/extensions)
+
+Doc Sections
+------------
+
+- [Authoring](https://github.com/Azure/azure-cli/blob/dev/doc/extensions/authoring.md) - How to author and develop an extension
+
+- [Command Guidelines](https://github.com/Azure/azure-cli/blob/dev/doc/command_guidelines.md) - Command Guidelines
+
+- [Publishing](https://github.com/Azure/azure-cli/blob/dev/doc/extensions/publishing.md) - How to publish an extension
+
+- [Summary Guidelines](https://github.com/Azure/azure-cli/blob/dev/doc/extensions/extension_summary_guidelines.md) - Summary guidelines for extensions to be published
+
+- [Extension Metadata](https://github.com/Azure/azure-cli/blob/dev/doc/extensions/metadata.md) - How to add additional extension metadata
+
+- [FAQ](https://github.com/Azure/azure-cli/blob/dev/doc/extensions/faq.md) - Commonly asked questions