Removes gatsby-plugin-offline, adds offline page + PWA compliant app

Author: thandaanda

package.json

@@ -15,7 +15,7 @@
     "react-dom": "^16.13.0"
   },
   "dependencies": {
-    "@draftbox-co/gatsby-wordpress-theme-libre": "^1.0.37",
+    "@draftbox-co/gatsby-wordpress-theme-libre": "^1.0.38",
     "dotenv": "^8.2.0",
     "gatsby": "2.20.24",
     "gatsby-plugin-crisp-chat": "^3.2.2",