Warp vulnerable to Path Traversal via Improper validation of Windows paths

Path resolution in warp::filters::fs::dir 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.