FIX: make composer full screen shortcut work when inputs have focus (#6907)

- Uses a Mousetrap plugin for global shortcuts
- Implemented for search `ctrl+alt+f` and composer fullscreen `shift+f11` shortcuts

lib/tasks/javascript.rake

@@ -73,6 +73,8 @@ task 'javascript:update' do
       destination: 'moment-locale',
     }, {
       source: 'moment-timezone/builds/moment-timezone-with-data.js'
+    }, {
+      source: 'mousetrap/plugins/global-bind/mousetrap-global-bind.js'
     }, {
       source: 'resumablejs/resumable.js'
     }, {