fix(Menu): Fix File -> Quit menu entry (#888) @dabalroman

Sience last update "Quit" option under File menu item isn't working.
It's probably because lines 647 - 649 were removed from Menu.js in f720d30.

Author: dabalroman

src/lib/Menu.js

@@ -589,6 +589,9 @@ export default class FranzMenu {
         {
           label: intl.formatMessage(menuItems.quit),
           role: 'quit',
+          click: () => {
+            app.quit();
+          },
         },
       ],
     });