Document proposed alt_text properties.

[transplier]

Proposed change

Added alt_text property support to cards which feature images. Please see home-assistant/frontend#14405

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 alt attribute to various images frontend#14405
• Link to parent pull request in the Brands repository: n/a
• This PR fixes or closes issue: fixes Update hassos_faq.markdown #14178 in frontend

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.

[frenck]

There are unrelated commit in this PR, probably caused by this PR being branched from the current branch.

Please git rebase your commit onto the next branch to clean this PR up.

Thanks 👍

../Frenck

[transplier]

Shoot, yes, silly of me. Fixing.

Branch has been rebased properly to next