fix: create directory if path is passed

[WolffRuoff]

Description

This PR fixes issue #1787 by checking in Fs::write_file if a directory was passed. If so, it calls create_dir_all to add any missing directories.

Questions

• While working on this issue, I noticed that this statement is repeated twice. I'm not sure if this is intentional, but if not I can remove the duplicate one in this PR as well.
• In the contributing guidelines, I see that it recommends creating tests to verify the fix, but I don't see any tests for this file. Is it ok if I write the tests directly in the file consistent to how url.rs does?

[jonathanrainer]

Hi @WolffRuoff thanks so much for this PR, we've just merged #1944 which I think solves this one? If that's the case are you ok for me to close this PR now?

[WolffRuoff]

Hi @jonathanrainer, sounds good 😄