Proposed change

Add documentation for calendar trigger initial version. The trigger currently only supports start time triggers and no offsets yet, but the interesting part is describing the updated calendar data model.

Note: This is a draft since frontend support has not yet been added, but starting the PR for referencing as development proceeds.

Type of change

• Spelling, grammar or other readability improvements (current branch).
• Adjusted missing or incorrect information in the current documentation (current branch).
• Added documentation for a new integration I'm adding to Home Assistant (next branch).
  • I've opened up a PR to add logo's and icons in Brands repository.
• Added documentation for a new feature I'm adding to Home Assistant (next branch).
• Removed stale or deprecated documentation.

Additional information

• Link to parent pull request in the codebase: Add initial implementation of a calendar trigger core#68674 and Add automation editor for calendar trigger frontend#12343 Add calendar event end trigger core#70372 Add calendar event end trigger to automation editor frontend#12389
• Link to parent pull request in the Brands repository:
• This PR fixes or closes issue: fixes #

Checklist

• This PR uses the correct branch, based on one of the following:
  • I made a change to the existing documentation and used the current branch.
  • I made a change that is related to an upcoming version of Home Assistant and used the next branch.
• The documentation follows the Home Assistant documentation standards.