pydicom 2.2 release candidate

[Darcy Mason]

Hi everyone,

A release candidate for pydicom v2.2.0 (v2.2.0-rc.1) has been posted to PyPi.  

Release notes are at https://pydicom.github.io/pydicom/dev/release_notes/index.html#version-2-2-0

We encourage people to install (`pip install --pre pydicom`) and report any issues to the discussion page.

Final v2.2.0 should be released within a few days if all goes well.

Thanks

Darcy