✨(frontend) add offline mode support

Add a offline mode support from a service worker.
The service worker will cache the assets and the
visited pages to be able to work offline.
Created a fallback page for when the user is offline
and tries to access a page that is not cached.

CHANGELOG.md

@@ -18,6 +18,7 @@ and this project adheres to
 - (frontend) add user to a document (#52)
 - (frontend) invite user to a document (#52)
 - (frontend) manage members (update role / list / remove) (#81)
+- ✨(frontend) offline mode (#88)
 
 ## Changed