[doc] extend example for building service worker with webpack

README.md

@@ -69,7 +69,7 @@ plugins: [
 ...
 ````
 
-### build with webpack
+### build service worker with webpack
 ````
 // webpack.config.js
 const InjectAssetsPlugin = require('@mightyplow/inject-assets-webpack-plugin');
@@ -77,13 +77,29 @@ const InjectAssetsPlugin = require('@mightyplow/inject-assets-webpack-plugin');
 ...
 
 entry: {
+    // build the app and the service worker with webpack
+    app: path.join(__dirname, 'src', 'index.js'),
     serviceWorker: path.join(__dirname, 'src', 'serviceWorker.js')
 },
 
 plugins: [
     new InjectAssetsPlugin({
-        targets: ['serviceWorker']
+        // replace assets in the service worker and in the app script
+        targets: ['serviceWorker', 'app']
     })
 ]
 ...
 ````
+
+````
+// index.js
+
+if ('serviceWorker' in navigator) {
+    // {{serviceWorker}} will be replaced with the built file name 
+    navigator.serviceWorker.register('{{serviceWorker}}')
+        .then((registration) => {
+            console.info('service worker registered');
+        });
+}
+
+````