Formatting toolbar buttons for the Collaborative Editor

[raimohanska]

Now with the Quill editor in place it is easy to add new toolbar buttons in the context menu for common formatting.

[raimohanska]

One just needs to figure out the communication channel between the context menu and Quill.

Optimally the buttons would react to the editor as well - for instance, Bold would be active when the selected text is bold.

Minimally, the toolbar buttons need to be shown when a crdt text item is selected and the button commands relayed to Quill.

[raimohanska]

Added in d4f7cf5 - only for the collaborative Quill editor though.