Provide a notebook SDK

[JacksonKearl]

Create documentation for creating notebook extensions, with helpful code samples and examples of how to create providers which perform common actions.

See webview/custom editor docs for examples.

[rebornix]

Some inputs might be helpful

• Background / Design
  • rendering & API thoughts Notebook rendering approaches and API vscode#88243
  • layout Notebook output security rebornix/notebook-test#3
• Current API status
  • tracking issue Notebook output security rebornix/notebook-test#3
• Samples
  • Jupyter compliant content provider
  • Renderer starter kit
  • Sample rich renderer nteract
  • Sample content provider for renderer for regex
  • Commands and keymaps