[PLT-6697] Added CTRL/CMD+SHIFT+K shortcut to open 'more direct messages' dialog (#6534)

* add keypress shortcut to open 'more direct messages' dialog

* removed duplicate e.preventDefault()

* add text description to /shortcuts output

i18n/en.json

@@ -799,6 +799,10 @@
     "id": "api.command_shortcuts.nav.switcher_team",
     "translation": "{{.CmdOrCtrl}}+ALT+K: Open a quick team switcher dialog\n"
   },
+  {
+    "id": "api.command_shortcuts.nav.direct_messages_menu",
+    "translation": "{{.CmdOrCtrl}}+SHIFT+K: Open direct messages menu\n"
+  },
   {
     "id": "api.command_shortcuts.nav.unread_next",
     "translation": "ALT+SHIFT+DOWN: Next channel or direct message in left hand sidebar with unread messages\n"