add prepublish hook

Author: yyx990803

package.json

@@ -13,7 +13,8 @@
     "build": "tsc -p .",
     "example": "npm run build && webpack --config example/webpack.config.js",
     "dev": "webpack --config example/webpack.config.js --watch",
-    "test": "npm run build && webpack --config test/webpack.config.js && mocha test/test.build.js"
+    "test": "npm run build && webpack --config test/webpack.config.js && mocha test/test.build.js",
+    "prepublish": "npm run build"
   },
   "repository": {
     "type": "git",