fix(#6): Ensure install button is hidden when PWA cannot be installed

6 add service worker so it can be used offline and installed as a pwa

src/styles/main.scss

@@ -28,3 +28,7 @@ text{
   -webkit-transform:translate(0,-50%);
           transform:translate(0,-50%);
 }
+
+#install-offline-app {
+  display: none;
+}

webpack.prod.js

@@ -1,4 +1,4 @@
-const merge = require('webpack-merge');
+const { merge } = require('webpack-merge');
 const { InjectManifest } = require('workbox-webpack-plugin');
 const common = require('./webpack.common');