➕(y-provider) add BlockNote server utils and yjs

Needed dependencies to mimic frontend code when generating a
document from a markdown string.

Will be used in the upcoming commits.

src/frontend/servers/y-provider/package.json

@@ -16,12 +16,14 @@
     "node": ">=18"
   },
   "dependencies": {
+    "@blocknote/server-util": "0.20.0",
     "@hocuspocus/server": "2.14.0",
     "@sentry/node": "8.41.0",
     "@sentry/profiling-node": "8.41.0",
     "express": "4.21.1",
     "express-ws": "5.0.2",
-    "y-protocols": "1.0.6"
+    "y-protocols": "1.0.6",
+    "yjs": "13.6.20"
   },
   "devDependencies": {
     "@hocuspocus/provider": "2.14.0",