Implement minimized action to hide the application on close (#60)

* Implement minimzed action to hide the application on close instead of
closing it.

* Add close event on the tray icon

* Add all items in the menu (not only Show/Close app)

* Changes on mainWindow. Toggle instead of Open/Close pair button

src/constants/settings.js

@@ -26,6 +26,7 @@ const settings = {
     width: "windowBounds.width",
     height: "windowBounds.height",
   },
+  minimizeOnClose: "minimizeOnClose",
 };
 
 module.exports = settings;