Show syntax errors on the playground (#12083)
## Summary
This PR updates the playground to show syntax errors.
(I forgot to update this and noticed it this morning.)
## Test Plan
Build the playground locally and preview it:
<img width="764" alt="Screenshot 2024-06-28 at 11 03 35"
src="https://github.com/astral-sh/ruff/assets/67177269/1fd48d6c-ae41-4672-bf3c-32a61d9946ef">
