Add only-project option to compilerOptions.runes

[notramo]

Please add an option to enable runes-only mode only for project files, but not for NPM libraries. Currently, many NPM libraries fail because runes mode is not supported by them, but project authors may want to enable runes mode for every file in their project.

[dominikg]

you should be able to use https://github.com/sveltejs/vite-plugin-svelte/blob/main/docs/config.md#dynamiccompileoptions

like

vitePlugin:{
  dynamicCompileOptions({filename}){
    if(!filename.includes('node_modules')){
      return {runes: true}
    }
  }
}

in svelte.config.js

[notramo]

This works. However, it seems like a common use case, so I recommend adding it to the docs.