Support Svelte 4 + 5

[leekeh]

Svelte v4+ is not supported in Sandpack. When I try to override the svelte template, I get Unsupported Svelte version. This seems to be an issue in the bundler, but this is greatly impacting my ability to use this project 🙏 .

[CompuIves]

Thanks for the report! I think this is the same issue as #1235, I will close it as duplicate.

I am looking into this. Svelte fundamentally changed, so need to do some work to make it work.