Add missing features for appearance CSS property

[queengooborg]

This PR adds the missing features of the appearance CSS property. The data comes from the mdn-bcd-collector project (v10.9.0).

Check out the collector's guide on how to review this PR.

Tests Used: https://mdn-bcd-collector.gooborg.com/tests/css/properties/appearance

[Elchi3]

This will break references made in web-platform-dx/web-features#634 cc @foolip

I think we can follow up with a fix to web-features (or we use tags, or we do both).

[queengooborg]

The idea of using web-features tags is to eliminate the need for WebDX to define all the BCD keys manually, is that correct? Tags sounds like the right call here!

[Elchi3]

The idea of using web-features tags is to eliminate the need for WebDX to define all the BCD keys manually, is that correct?

Yes, that was the whole reason I wanted tags! :)

[foolip]

This will break references made in web-platform-dx/web-features#634 cc @foolip

I think we can follow up with a fix to web-features (or we use tags, or we do both).

Feel free to break web-features references. They'll all come to light when we compute Baseline status from BCD, and I can fix things then. If you want to fix things proactively that's nice, but I don't want web-features to slow down BCD maintenance.

[queengooborg]

I've added a tag with the name matching the feature group, so that should help!