Update zha.markdown to answer repeated question about supported devices

[Gamester17]

Proposed change

Updated the zha.markdown to answer a repeated community question about supported devices and device compatibility for ZHA.

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: Not applicable.
• Link to parent pull request in the Brands repository: Not applicable.
• This PR fixes or closes issue: Not applicable.

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.
• The documentation follows the Home Assistant documentation standards.

[frenck]

Thanks, @Gamester17 👍