[D8][UX] Text format configuration form: render CKEditor settings as vertical tabs

[klonos]

This configuration form can get really long, which requires a lot of scrolling in order to get an overview of settings:

In D8 they have the settings in vtabs, which results in a more compact form:

Sounds like a good idea to me.

Wonder what @jenlampton thinks... She hasn't been a fan of vertical tabs in the past.