Consider removing underline and strikethrough styles #399
Description
These styles:
- Do not affect layout
- Could be implemented on top of Parley without dedicated support
- Require unnecessary (and expensive) full rebuilds of the layout if they change (when such a change should really only require a "repaint").
The way to implement underline/strikethrough if we remove the dedicated styles would be to associate an ID with a span of text using the "brush" style. The styles associated with that ID can then be updated without causing a relayout.
The alternative would be to keep the dedicated styles but allow them to be updated without triggering a relayout.