Memory view support

[romainthomas]

Thank you for making this new library!

Would it make sense to have a nb::memoryview in nanobind?

I tried to workaround with ndarray without success so if the memoryview aims being supported, I will be happy to draft a PR for that.

[wjakob]

My first reaction is that we probably don't want a separate interface just specific to memoryview. It seems that ndarray could be updated to deal with it as well. This isn't on my priority list, so your help is welcomed if the feature is important to you.