Qt: List changes between current->latest build in auto updater

Thanks to @hhromic for the API endpoint tip.

src/duckstation-qt/autoupdaterdialog.h

@@ -28,6 +28,9 @@ private Q_SLOTS:
   void getLatestTagComplete(QNetworkReply* reply);
   void getLatestReleaseComplete(QNetworkReply* reply);
 
+  void queueGetChanges();
+  void getChangesComplete(QNetworkReply* reply);
+
   void downloadUpdateClicked();
   void skipThisUpdateClicked();
   void remindMeLaterClicked();