Change the sanitization function to a asyncio.to_thread

[EvieePy]

Description

Allows bleach to run in a asyncio.to_thread.

Checklist

• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
  • I have updated the changelog with a quick recap of my changes.
• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• This PR is not a code change (e.g. documentation, README, ...)
• I have read and agree to the Developer Certificate of Origin for this contribution

[LostLuma]

Might be better to highlight all files at once in a single asyncio.to_thread call instead?

[EvieePy]

Might be better to highlight all files at once in a single asyncio.to_thread call instead?

Yeah this makes sense