tower-http's improper validation of Windows paths could lead to directory traversal attack

tower_http::services::fs::ServeDir didn't correctly validate Windows paths, meaning paths like /foo/bar/c:/windows/web/screen/img101.png would be allowed and respond with the contents of c:/windows/web/screen/img101.png. Thus users could potentially read files anywhere on the filesystem.

This only impacts Windows. Linux and other unix likes are not impacted by this.