Add upgrade script for adding sub content id

upgrades.js

@@ -0,0 +1,21 @@
+var H5PUpgrades = H5PUpgrades || {};
+
+H5PUpgrades['H5P.QuestionSet'] = (function ($) {
+  return {
+    1: {
+      4: function (parameters, finished) {
+        for (var i = 0; i < parameters.questions.length; i++) {
+          if (parameters.questions[i].subContentId === undefined) {
+            // NOTE: We avoid using H5P.createUUID since this is an upgrade script and H5P function may change in the
+            // future
+            parameters.questions[i].subContentId = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(char) {
+              var random = Math.random()*16|0, newChar = char === 'x' ? random : (random&0x3|0x8);
+              return newChar.toString(16);
+            });
+          }
+        }
+        finished(null, parameters);
+      }
+    }
+  };
+})(H5P.jQuery);