Enable using a function with useful arguments for the custom scaffolding feature

[acidoxee]

In the Vite plugin, in the customScaffolding field, all of its subfields can only be strings for now.

It would be great to be able to provide a function that returns a string instead, with rich arguments provided by TanStack Router, such as the file or route path, to customize the output. For instance, based on the path, we could produce tailored component names instead of a generic one like RouteComponent (people tend to overlook this and forget to rename it).