🐧 🐛 Workaround for electron/electron#5050

Chromium only show the Tray icon with libappindicator when the env `XDG_CURRENT_DESKTOP`'s value is `Unity`. But under elementaryOS its value is 'Pantheon'.

Set it to `Unity` before app startup make the tray icon show under elementaryOS.

lib/common/init.js

@@ -58,3 +58,8 @@ if (process.platform === 'win32') {
     process.windowsStore = true
   }
 }
+
+// Workaround for electron/electron#5050
+if (process.platform === 'linux' && process.env.XDG_CURRENT_DESKTOP === 'Pantheon') {
+  process.env.XDG_CURRENT_DESKTOP = 'Unity';
+}