billy.File interface is missing Stat() for io/fs compatibility

[jmgilman]

The io/fs package defines a File interface as such:

type File interface {
	Stat() ([FileInfo](https://pkg.go.dev/io/fs#FileInfo), [error](https://pkg.go.dev/builtin#error))
	Read([][byte](https://pkg.go.dev/builtin#byte)) ([int](https://pkg.go.dev/builtin#int), [error](https://pkg.go.dev/builtin#error))
	Close() [error](https://pkg.go.dev/builtin#error)
}

When attempting to interface with a third-party package that uses this interface, I noticed I could not pass a billy.File because it's missing the Stat() method. This seems like an oversight.

[pjbgf]

@jmgilman have you tried this with the latest from main? The File interface was updated recently and now includes fs.File. This will be released on the next major release v6, release date is still TBC.