Fix #26

XSS vulnerability caused by filenames (or /f/ urls)

https://github.com/MayhemYDG/4chan-x/commit/f4592eec4141135f6c4da868db6b1d3a6ad21a58
https://github.com/MayhemYDG/4chan-x/commit/b8debe756af71a375f8e34e880612bc1eb0dff50