Adopt CSS Typed OM API for Internal Styling

[vincentriemer]

Moving to the CSS Typed OM API instead of what is currently done with just the style property on HTMLElements should improve both styling performance (no need to serialize styles to a string just to have the browser parse that string to apply it) and maintainability with a more structured/typed API.

It may be a tad to early to start work but it could be started soon as https://github.com/csstools/css-typed-om stabilizes.