Shortcut menu should be context-senstive

The shortcut menu (accessible from either ? or the hamburger menu contains a list of every keyboard shortcut within the Discourse environment. However, not all the shortcuts shown are applicable in all cases. For example x-t and x-r (dismiss topics and discmiss new) after using g-u (jump to unread) or explitily going to unseen (putting /unseen at the end of the url). This leads to user confusion and frustration. Only the applicable options should be included on the menu.