Adds a section on container-specific considerations for Binsparse.
Asking for help:

• @BenBrock I think we might want to add some language about datatypes in HDF5, is that right?
• @hameerabbasi Could you add a section on in-memory considerations, or at least a link?
• @ivirshup Do you agree with the way I've laid out npy files? npz files are a little messier to work with so I didn't use them, but if you think that's the more correct way to go I'd like to hear your feedback. Also, do you think you'd like to add a section on zarr?