`tauri_plugin_localhost` doesn't work in dev mode

When running `npm run tauri dev` on linux and using the `tauri_plugin_localhost` example code, nothing loads in the localhost-served window. However, this works correctly in a fully built binary.

This appears to be because, unlike when the app is fully built, the path `/` does not resolve to `/index.html`.

Adding

```
let path = if path == "/" {
"/index.html".to_string()
} else {
path
};
```
after https://github.com/tauri-apps/plugins-workspace/blob/fe23a5e01399a6ad61426bf8a94a6bb97227cf88/plugins/localhost/src/lib.rs#L90 appears to serve files that have been already built with `vite build`, but I am not sure how to forward the files from vite's dev server.