Feature: allow manual specification of the ZIP directory structure

[AshesITR]

It would be fantastic to allow for manual specification of the ZIP directory structure in a zip::zipr or zip::zipr_append call, e.g.

zip::zipr("myzip.zip", files = list("myfile.txt" = "myfile-on-disk.txt"))

I skimmed the code and think it shouldn't be too hard by changing the key in get_zip_data() if names are present.
I can give it a try if you think that feature would be useful.

Ideally:

• for plain files, the name directly translates to the key
• for directories, the name replaces the key up to the specific directory (so the subdirectories and files have the same relative structure, just a different parent name / path)

[gaborcsardi]

Yeah, I think that would be pretty cool. A PR is welcome.

[AshesITR]

@gaborcsardi are you still interested in this feature? If so, I can try rebasing #51 onto current main.

[gaborcsardi]

Yes, sorry for the wait. I'll look at it soon, before the next release.