Polish Electron desktop shell

package.json

@@ -38,6 +38,7 @@
   "build": {
     "appId": "app.ruwio.desktop",
     "productName": "RUWIO",
+    "icon": "icon.png",
     "directories": {
       "output": "release"
     },
@@ -46,6 +47,12 @@
       "dist-electron/**/*",
       "package.json"
     ],
+    "extraResources": [
+      {
+        "from": "build/icon.png",
+        "to": "build/icon.png"
+      }
+    ],
     "linux": {
       "target": [
         "AppImage"