When I runpnpm build I get the following error:

Error: 404 /tutorial/ondestroy (linked from /tutorial/auto-subscriptions)

There are two ways to fix it.

1. remove that link (fix: remove link for removed page #315)
2. revert removedonDestroy exercise, and make it simpler (chore: simplify the onDestroy exercise #316)

I personally recommend 2, because for someone like me who comes from other programming languages, I learned a lot from theonDestroy exercise.
Indeed, theonDestroy exercises were complex, but I think it can be made simpler.

I have created two different PRs (as Draft just to avoid both being merged).
Please merge the one that is more suitable.