Address UX issues around toolbar

There are a few things we should address with regards to the toolbar:

[ ] When I hover over the top of the side-bar, the ‘eye’ and ‘comment’ icons appear. It’s not immediately clear what these icons do but it’s good that you have a tooltip. The tooltip is a little slow to appear.
[ ] The tooltip doesn’t change when you have turned on the annotations. It still says ‘show annotations’.
[ ] The feedback when annotations are on/off is quite subtle. You could use a different icon to indicate highlights are off.
[ ] For consistency and discoverability it might be better if these icons are always visible on the minimised toolbar.
[ ] It might also be worth re-positioning these icons. Once the side-bar is open and there are comments above the current location in the page, the comment icon sits on top of the marker which indicates the number of comments e.g.

hypothesis / vision