small fix for tanstack start supabase example

[galarus]

The dev environment will build and run but not allow posts to be viewed. It appears that redaxios is missing from the dependencies in the tanstack start supabase example. It is also lacking a README, but maybe there is a reason for that. I wasn't sure how or if this was an appropriate thing to make a pull request for.

[schiller-manuel]

sure, PRs are welcome!