booklore: add note for start-up in frontend (#7331)

Author: MickLesk

frontend/public/json/booklore.json

@@ -31,5 +31,10 @@
     "username": null,
     "password": null
   },
-  "notes": []
+  "notes": [
+    {
+      "text": "Starting Booklore (Web UI) may take up to 2 minutes after a restart or fresh installation.",
+      "type": "info"
+    }
+  ]
 }