StaticFile can't be compared with `<`

[tim-schilling]

There's a bug with what's on the main branch where the sorted(used_paths) raises an exception about not being able to compare two StaticFile instances. It can be solved by adding @dataclass(..., order=True) to the decorator.

[matthiask]

Oh, that's bad. Our test only has a single static file, that's why this wasn't triggered.