Enable installing app as pwa

app/views/service_worker/manifest.json.erb

@@ -0,0 +1,21 @@
+{
+  "short_name": "Zdravo Stopalo",
+  "name": "Zdravo Stopalo",
+  "icons": [
+    {
+      "src": "<%= image_path('icon-192.png')%>",
+      "type": "image/png",
+      "sizes": "192x192"
+    },
+    {
+      "src": "<%= image_path('icon-512.png')%>",
+      "type": "image/png",
+      "sizes": "512x512"
+    }
+  ],
+  "start_url": "<%= root_path %>",
+  "background_color": "#FFFFFF",
+  "display": "standalone",
+  "scope": "<%= root_path %>",
+  "theme_color": "#8e2731"
+}

app/views/service_worker/service_worker.js

@@ -0,0 +1,14 @@
+function onInstall(event) {
+  console.log("[Serviceworker]", "Installing!", event);
+}
+
+function onActivate(event) {
+  console.log("[Serviceworker]", "Activating!", event);
+}
+
+function onFetch(event) {
+  console.log("[Serviceworker]", "Fetching!", event);
+}
+self.addEventListener("install", onInstall);
+self.addEventListener("activate", onActivate);
+self.addEventListener("fetch", onFetch);