Add unsupported help for systemd-resolved

[mdegat01]

Proposed change

New unsupported OS reason added to supervisor, adding the corresponding help page for users with this issue.

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 unsupported message if no systemd-resolved supervisor#3487
• 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.

[frenck]

The releases of the Supervisor are out of sync with the Home Assistant Core, this PR should probably target the current branch for that reason (this can go live in the current documentation without problems anyways).

[mdegat01]

ugh. bad rebase, sorry all

[frenck]

Thanks, @mdegat01 👍