Where can newbies upload their non-working extensions?

Newbies can’t attach files to their posts.
So when they’ve written an extension that “doesn’t work”, they need to paste the code into their posts.
Which is apparently a hard problem.
And even when they do get it right, we need to copy and paste the code into files on our computers, before we can try it out.

There has to be a simpler way.
Are there websites where newbies can upload small ZIP files, preferably without registration?