update build script for cross-platform

Author: HyunmoAhn

README.md

@@ -11,10 +11,16 @@ You can use every web content though widget in wallpapers
 ```
 // if you use yarn
 
-yarn build
+yarn build:window // use window OS
+yarn build:mac // use macOS
+yarn build:linux // use linux
 
 // else
-npm run build
+npm run build:window // use window OS
+npm run build:mac // use macOS
+npm run build:linux // use linux
+
+then open dist directory and install oh-my-desk.exe (or .dmg)
 ```
 
 **when develop**

package.json

@@ -4,7 +4,9 @@
   "description": "desktop widget application",
   "main": "main.js",
   "scripts": {
-    "build": "yarn build:app && cross-env NODE_ENV=production electron-builder --win",
+    "build:window": "yarn build:app && cross-env NODE_ENV=production electron-builder --win",
+    "build:mac": "yarn build:app && cross-env NODE_ENV=production electron-builder --mac",
+    "build:linux": "yarn build:app && cross-env NODE_ENV=production electron-builder --linux",
     "build:app": "cross-env NODE_ENV=production webpack --config webpack.prod.config.js",
     "watch": "watchify app/app.js -o build/bundle.js -t babelify -v",
     "dev": "NODE_ENV=development ./node_modules/.bin/electron .",