Add single mas build script

Author: kevinsawicki

package.json

@@ -18,7 +18,7 @@
     "package": "npm run pack-mac && npm run pack-win && npm run pack-linux",
     "installer": "node ./script/installer.js",
     "windows-store": "node ./script/windows-store.js",
-    "mas": "electron-packager . --asar --overwrite --platform=mas --arch=x64 --icon=assets/app-icon/mac/app.icns --prune=true --out=out --osx-sign.identity='Developer ID Application: GitHub' --extend-info=assets/mac/info.plist",
+    "mas": "./script/mas.sh",
     "prepare-release": "npm run package && npm run sign-exe && npm run installer && npm run sign-installer",
     "release": "node ./script/release.js"
   },

script/mas.sh

@@ -1,5 +1,17 @@
 #!/bin/bash
 
+set -ex
+
+electron-packager . \
+  --asar \
+  --overwrite \
+  --platform=mas \
+  --arch=x64 \
+  --icon=assets/app-icon/mac/app.icns \
+  --prune=true \
+  --out=out \
+  --extend-info=assets/mac/info.plist
+
 # Name of your app.
 APP="Electron API Demos"