Change base url

[razzeee]

Hey I've needed to move the base url of my app via https://developer.mozilla.org/en-US/docs/Web/HTML/Element/base

Now keystatic seems to not handle that well and does not fetch correctly and it seems like the frontend breaks after the initial loading too.

You can test with this https://github.com/CTreffOS/ctreffos-website-astro but you will need to add keystatic first