Ensure that `index.html` is bundled into `dist`

This is necessary for our "Production and Deployment" chapter of the book.

package.json

@@ -30,6 +30,7 @@
     "hello-wasm-pack": "^0.1.0",
     "webpack": "^4.16.3",
     "webpack-cli": "^3.1.0",
-    "webpack-dev-server": "^3.1.5"
+    "webpack-dev-server": "^3.1.5",
+    "copy-webpack-plugin": "^4.5.2"
   }
 }
\ No newline at end of file

webpack.config.js

+const CopyWebpackPlugin = require("copy-webpack-plugin");
 const path = require('path');
 
 module.exports = {
@@ -7,4 +8,7 @@ module.exports = {
     filename: "bootstrap.js",
   },
   mode: "development",
+  plugins: [
+    new CopyWebpackPlugin(['index.html'])
+  ],
 };