🐛(frontend) fix initial content with collaboration

The way the initial content was created was causing
issues with the collaboration server.
As soon a user started typing, the problem was gone.
This commit fixes that by letting Blocknote
managing the initial content, then we update the
Blocknote initial content with our initial content.

CHANGELOG.md

@@ -24,6 +24,7 @@ and this project adheres to
 
 ## Fixed
 
+- 🐛(frontend) fix initial content with collaboration #484
 - 🐛(frontend) Fix hidden menu on Firefox #468
 - 🐛(backend) fix sanitize problem IA #490