[svelte-loader] Support Svelte 5

[bhark]

Is your feature request related to a problem? Please describe.
Svelte 5 is (mostly) backwards compatible, and as such I imagine extending support shouldn't be a major issue. At the moment, I have not been able to implement visual editing with a simple Svelte 5 application using @sanity/svelte-loader. I haven't attempted a setup without svelte-loader.

Describe the solution you'd like
I'd like to be able to follow the integration guide and end up with a working visual editing tool.

Describe alternatives you've considered
Installing with --legacy-peer-deps. I end up having to install react, and the implementation is too broken to work around. I end up with errors such as:

Error: Build failed with 2 errors: node_modules/@sanity/visual-editing/dist/_chunks-es/PointerEvents.js:1:528: ERROR: Could not resolve "react-dom" node_modules/@sanity/visual-editing/dist/_chunks-es/renderVisualEditing.js:1:102: ERROR: Could not resolve "react-dom/client"

Additional context
Svelte 5 has been the go-to production version for some time now. It would be fitting to support it, and update the docs to go along with the new support.

[rdunk]

Closing as dupe of #2075.

I believe we plan on adding support soon, but as far as I'm aware Svelte 5 has only been stable for about a month or so.

Just as a point of clarification, React will stay as a dependency as it is used to render overlays regardless of the framework implementation.