Improved text editor

[raimohanska]

Things that would be nice

• Automatic bulleted lists
• Checkbox support
• Basic formatting toolbar (italic, bold, underline)
• Editing in markdown mode

[raimohanska]

Working on this in #240 - the Quill editor will have at least automatic bulleted lists out of the box.

[raimohanska]

Quill collaborative editor is now enabled as an opt-in feature for authenticated users when creating a new board.

There's no markdown though. Checkboxes could maybe be implemented using quill-task-list.

Toolbar buttons should be rather easy, and actually covered in this issue: #245