More responsive toolbar

Problem/Motivation

Current toolbar can be large with a lot of enabled islands, the end part an be very long, as well as start part in some cases.

Note: we don't want a phone support, but at least a proper 1024 when there is a lot of islands enabled.

Proposed resolution

We should have a more responsive version:

Switch start button group to a dropdown.
Switch end islands buttons or dropdown in a main end dropdown.

Icons and text to define.

From my perspective this should be done mostly with js/css, but we probably need a build to have the dropdown container component.
Note: there is already a small script to reduce the size of buttons, it's a starting point: components/toolbar/toolbar.js