Explain special values for MQTT numeric sensor

[jbouwh]

Proposed change

Explain special values for MQTT numeric sensor:
When device_class, state_class, unit_of_measurement or suggested_display_precision is set:

• '' values will be ignored.
• None values will make the sensor

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: Fix handling None or empty value for numeric MQTT sensor core#87004
• 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]

✅ Approved. Can be merged as soon as the parent PR gets merged.

[jbouwh]

Set to draft as it likely this PR is changed.

[jbouwh]

@frenck PR is in wrong queue, parent PR is merged

[frenck]

Thanks, @jbouwh 👍

../Frenck