[Electron] MacOs and MessageBox fix

MacOS:
- Nice icon for DMG
- Fix bug when Configurator was minimized and dock icon is clicked

Fix (Workaround):  After a MessageBox (alert()) was displayed, all input fields stopped working.

js/gui.js

@@ -1,4 +1,6 @@
 'use strict';
+const { dialog } = require("@electron/remote");
+
 
 const CONFIGURATOR = require('./data_storage');
 const Switchery = require('./libraries/switchery/switchery')
@@ -529,6 +531,13 @@ GUI_control.prototype.update_dataflash_global = function () {
     }
 };
 
+/**
+* Don't use alert() in Electron, it has a nasty bug: https://github.com/electron/electron/issues/31917
+*/ 
+GUI_control.prototype.alert = function(message) {
+    dialog.showMessageBoxSync({ message: message, icon: "./images/inav_icon_128.png" });
+}
+
 // initialize object into GUI variable
 var GUI = new GUI_control();