doc: add cosmosdb events doc

[mydiemho]

What did you implement

Azure plugin now supports CosmosDB binding. Updated the docs to show how to use it.

How can we verify it

Documentation change.

Todos

Useful Scripts

• npm run test-ci --> Run all validation checks on proposed changes
• npm run lint-updated --> Lint all the updated files
• npm run lint:fix --> Automatically fix lint problems (if possible)
• npm run prettier-check-updated --> Check if updated files adhere to Prettier config
• npm run prettify-updated --> Prettify all the updated files

• Write and run all tests
• Write documentation
• Enable "Allow edits from maintainers" for this PR
• Update the messages below

Is this ready for review?: YES
Is it a breaking change?: NO

[ganeshvlrk]