This improves bold text readability.
This has to be done in the actual element, in the TextEditor and on the 
properties panel.

The main components are right at top level and the directories below
mimic the data structure (unit->page->section).
The toolbar is only used in dev mode and does not belong directly to the
unit view.
The TextEditor is a complex component and deserves it's own directory
even though it is used within the unit-view. Might be refactored to its
own module later.

Based on TipTap which in turn is based on ProseMirror. No further assets 
are needed.