Close to tray (#21)

* Close to Tray implemented

* Enable Tray Icon on Linux

* Remove unnecessary function

* Revert 26a3a98e38

src/electron/electronConstants.ts

@@ -1,4 +1,5 @@
 export class ElectronConstants {
     static readonly enableMinimizeToTrayKey: string = 'enableMinimizeToTray';
+    static readonly enableCloseToTrayKey: string = 'enableCloseToTray';
     static readonly enableTrayKey: string = 'enableTray';
 }