add weixin js script

package.json

@@ -2,6 +2,8 @@
   "name": "ec",
   "version": "0.1.0",
   "private": true,
+  "homepage": ".",
+  "main": "src/index.js",
   "dependencies": {
     "@babel/core": "7.2.2",
     "@svgr/webpack": "4.1.0",

public/index.html

@@ -8,6 +8,7 @@
       content="width=device-width, initial-scale=1, shrink-to-fit=no"
     />
     <meta name="theme-color" content="#000000" />
+    <script src="https://res.wx.qq.com/open/js/jweixin-1.2.0.js"></script>
     <!--
       manifest.json provides metadata used when your web app is installed on a
       user's mobile device or desktop. See https://developers.google.com/web/fundamentals/web-app-manifest/