Add new radon device class

[jrbeilke]

Proposed change

Using the Airthings integration with an Airthings View Plus, which includes Radon monitoring, but Home Assistant lacks a device class for handling Radon sensor and units. Following some of the other examples (ie. #54075 for air quality devices) I've attempted to add a new Radon device class.

The Airthings API tracks Radon in becquerels (Bq/m³), but in the US picocuries (pCi/L) are more commonly used, and the new Radon device class for Home Assistant handles the conversion based on imperial vs metric units.
https://help.airthings.com/en/articles/3119854-radon-what-is-the-difference-between-pci-l-and-bq-m3

Airthings has a number of different devices now for tracking Radon (ie. Wave Radon, Wave Plus, and View Radon), and it would seem that other device integrations would benefit from this Radon device class as well.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• Link to documentation pull request: Add Radon device class developers.home-assistant#1208 and add Radon device class home-assistant.io#21562

Checklist

• The code change is tested and works locally.
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[homeassistant]

Hi @jrbeilke,

It seems you haven't yet signed a CLA. Please do so here.

Once you do that we will be able to review and accept this pull request.

Thanks!

[frenck]

Has this addition been approved via an architectural discussion?
This changes our entity model, and requires to be pre-approved before this can be added.

[jrbeilke]

Has this addition been approved via an architectural discussion?
This changes our entity model, and requires to be pre-approved before this can be added.

Ah missed that. Here is a new architectural discussion for adding a radon device class: home-assistant/architecture#732

[github-actions]

There hasn't been any activity on this pull request recently. This pull request has been automatically marked as stale because of that and will be closed if no further activity occurs within 7 days.
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