Support HTML and FontAwesome icons in key labels

[sunaku]

When I load this file into kle-ng, I notice that inline HTML and FontAwesome icons aren't rendering properly in key labels. 💁

• Actual appearance (with kle-ng app): ⚠️

• Expected appearance (with original KLE): ✅
  

Thanks for your consideration.

[adamws]

custom css is not supported.
Built-in KLE icon set is not supported either - I encourage users to use inline svgs

https://github.com/adamws/kle-ng?tab=readme-ov-file#compatibility

to add some context; due to major difference in rendering approach, I doubt that kle-ng will support custom css.
The original KLE approach regarding fontawesome is something I did not like and I'm not planning adding it either.