In the current version, all li element gets the tabindex 0 and the buttons are incorrectly getting the attribute tabindex -1.
Therefor the button are no longer operable via keyboard.
And this is also labeled as wrong behavior by various accessibility checkers.

The PR #86 should fix the Issue here.

It would be fantastic if you could do a review here soon @ranbuch.
We plan to update to the new version of the toolbar in Joomla! for the next release and would like to fix these bugs beforehand.
Many thanks in advance!