New accessor for bitpacking and unbitpacking binary/boolean DataArrays #11610

What is your issue?

As part of a larger project I've been working on, I created bitpacking/unbitpacking methods that utilize numpy's packbits/unpackbits functions under the hood, but stores and reads all the relevant information about what each bit represents and how the packing was done as metadata on an xarray.DataArray.

I recently extracted that code from the larger project it was in, and wrote it up as a DataArray accessor extension that is available here. I'm planning on uploading it to PyPI in the near future to make it easier to install, but also wanted to post it here.