build: add Linux AppImage target and dist:linux script

electron-builder.yml

@@ -15,3 +15,8 @@ win:
   target:
     - zip
   icon: build/icon.png
+linux:
+  target:
+    - AppImage
+  icon: build/icon.png
+  category: Game

package.json

@@ -8,10 +8,14 @@
   "scripts": {
     "start": "electron .",
     "dist": "electron-builder --win zip",
+    "dist:linux": "electron-builder --linux --publish never",
     "test": "node test/smoke.js"
   },
   "devDependencies": {
     "electron": "^40.10.2",
     "electron-builder": "^25.1.8"
+  },
+  "allowScripts": {
+    "electron@40.10.2": true
   }
 }