Fix default Mac shortcut

From
https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/commands

On Macs, "Ctrl" is interpreted as "Command", so if you actually need
"Ctrl", specify "MacCtrl".

app.js

@@ -75,7 +75,7 @@
         $translateMathBtn = $('<button id="translate_math" tabindex="-1" class="btn btn-icon"><i class="static-icon-copy"></i></button>');
         var shortcut;
         if(isMac)
-          shortcut = " (Cmd+C)" 
+          shortcut = " (Ctrl+C)"
         else
           shortcut = " (Alt+C)"
         title = "Copy Source & Translate Math " + shortcut

manifest.json

@@ -2,7 +2,7 @@
   "name": "Khan Academy Dots",
   "description": "Translate math notation in Khan Academy Crowdin strings.",
   "author": "Daniel Hollas & Szymon Bubak & Krzysztof Krystek & Robert Pala",
-  "version": "3.2.1",
+  "version": "3.2.2",
   "permissions": [
     "activeTab",
     "storage"
@@ -23,7 +23,7 @@
   "translate-math": {
     "suggested_key": {
       "default": "Alt+C",
-      "mac": "Ctrl+C"
+      "mac": "MacCtrl+C"
     },
     "description": "Click 'translate-math' button"
   }