Implement PWA features: add service worker, manifest, and offline page; enhance footer and header navigation

assets/manifest.json.html

@@ -0,0 +1,25 @@
+---
+permalink: /assets/manifest.json
+---
+
+{
+  "name": "{{ site.title }}",
+  "short_name": "CPRED",
+  "start_url": "{{ "/" | relative_url }}",
+  "display": "standalone",
+  "background_color": "#f8ef02",
+  "theme_color": "#ff003c",
+  "icons": [
+    {
+      "src": "{{ "/assets/img/icon-192.png" | relative_url }}",
+      "sizes": "192x192",
+      "type": "image/png"
+    },
+    {
+      "src": "{{ "/assets/img/icon-512.png" | relative_url }}",
+      "sizes": "512x512",
+      "type": "image/png"
+    }
+  ]
+}
+