[EPIC] Skaffold docs

[tejal29]

This issue is an EPIC for tracking all the docs work.

Docs:

• Improve documentation for skaffold diagnose #2465 - Skaffold diagnose docs ( Cancelled for this EPIC)
• Detailed Event API + Control API documentation on proto #1703 ( event api + control api)
  lets break it into 2
  • Event API docs ( in progress @tejal29)
  • Trigger api docs
• [Docs] Operating modes page should describe skaffold dev, run, debug modes. #3024 ( skaffold dev, run, debug docs)
• Make "Insecure Registries title linkable" here https://skaffold.dev/docs/concepts/image_repositories/ so we can use it in the feature matrix.
• Add docs for skaffold init. How to use and also fix Add "Getting started with your project" to Getting Started #2951
• Add docs on skaffold version command line
• Add Feature matrix in deprecation policy docs [In progress] add links to docs which are present #3026