Add keyboard shortcut for "Show annotations"

A user can create annotations by using the shortcut (Ctrl + M) without having to activate Annotation Settings (the configuration overlay from menu).
But every time the page is refreshed, the annotations are hidden and the user needs to go again through "Annotation Settings" -> "Show annotations", in order to contextual visualize them.

A keyboard shortcut that could toggle "Show annotations" would improve the productivity and the users wouldn't have to go through the menu or to use the mouse.