add utilities for creating zarr stores and groups

[Artur-man]

No description provided.

[Bisaloo]

I'll have a look at this in the coming weeks.

Please don't feel like you have to deal with keeping this branch in sync / resolving conflicts. I am creating them so I'm perfectly happy to resolve them.

[Artur-man]

ah no worries, I am learning some new tricks from you too. Good exercise!

[Bisaloo]

Hi @Artur-man, I rebased this on top of devel. This means that if you install from this branch, all the boxes listed in scverse/anndataR#190 should be checked.

Please let me know if anything else is needed.

[Artur-man]

Thanks so much @Bisaloo, really appreciate it!

I quickly asked folks in scverse/anndataR that if we should renew the PR that we sent them months ago, but yes this is a good start!

I will go over the PR/branch again after this and open other issues here if I (or somebody else) stumble on anything.