Change CONTRIBUTING.md to avoid UTF-16 encoding issue

[escritorio-gustavo]

The issue found yesterday about README.md having been encoded in UTF-16 is caused by running cargo readme > file_path on Windows.

Windows users should instead use cargo readme -o file_path

[NyxCode]

Thanks!
PS: I've sent you an email to your proton address, just in case you don't check that regularly.

[escritorio-gustavo]

Oh thanks for the heads up, I pretty much never check that lol, I'll go read it.