Explicitly include '?' as a fallback key for keyboard shortcuts

(closes #5675)

This allows for a localized version of the key,
but iD will still respond to the '?'

data/shortcuts.json

@@ -41,7 +41,7 @@
               "text": "shortcuts.browsing.help.help"
             },
             {
-              "shortcuts": ["shortcuts.toggle.key"],
+              "shortcuts": ["shortcuts.toggle.key", "?"],
               "text": "shortcuts.browsing.help.keyboard"
             },
             {

modules/ui/shortcuts.js

@@ -21,7 +21,7 @@ export function uiShortcuts(context) {
 
 
     context.keybinding()
-        .on(t('shortcuts.toggle.key'), function () {
+        .on([t('shortcuts.toggle.key'), '?'], function () {
             if (d3_selectAll('.modal-shortcuts').size()) {  // already showing
                 if (_modalSelection) {
                     _modalSelection.close();