Provide a more discoverable way to assign keyboard shortcuts

[aurimasv]

Without looking at the documentation (let's be honest, that's annoying), it's quite difficult to figure out how to assign keyboard shortcuts in Word.

I think we could add a "Zotero preferences" button (or something of the sort) to the ribbon that would open a window with global Zotero-related Word preferences. That could contain a reference to Keyboard shortcuts. It could also contain things like field code toggle, field code shading, etc. I guess it becomes a bit weird, since we also have Cite preferences in Zotero.

It should be possible to open the keyboard shortcut window and filter the list of macros to display only Zotero-related macros, since Record Macro window does something similar.