Add string view support

[WillAyd]

I've noticed polars in particular has started to export Arrow C data with the "vu" format string for string views, but I don't see any support for those in nanoarrow. Is this something that can be added easily? I think the same API we have in place for strings can be used for string views as well?

@bkietz probably knows more

[paleolimbot]

@jorisvandenbossche started a PR for this ( #367 ) and recently the cudf maintainers were asking about it as well. It is a little tricky because the assumption of a finite number of buffers runs deep in the existing array view logic but I think Joris handled most of that already. I was planning to assess the complexity of adding it in the near term but if you have any interest in taking a stab at all or part of it feel free!

[WillAyd]

Sounds good. Will take a look if I get some free time

[paleolimbot]

Great! No worries if you aren't able to get to it, but post a note here if you do so I don't step on your toes!