workflow to do pre-releases to pypi on commits to master

[asherf]

this is based on what moto and django-promethues are doing.
basically a pre-release is created on pypi on every push to master.
which means people don't have to wait for a release if they want to consume a patch that landed on master.
the pre-release GHA workflow file uses pypi's new trusted publisher feature and requires a simple config to be added on the pypi side.

@mpdavis lmk what you think.
I am also planning to have a different workflow file for regular releases, similar to what I did here
However, I don't have permissions to configure trusted publishers in pypi for this project (I don't have permissions to do it).
So I will need you to do it if you think it is a good idea to do and have some time to do it.
It is very simple to do. instructions are here: https://docs.pypi.org/trusted-publishers/adding-a-publisher/

[codecov]

Codecov Report

Merging #319 (b4a8dbe) into master (4b0701b) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #319   +/-   ##
=======================================
  Coverage   92.69%   92.69%           
=======================================
  Files          15       15           
  Lines        1424     1424           
=======================================
  Hits         1320     1320           
  Misses        104      104           

Impacted Files	Coverage Δ
jose/__init__.py	100.00% <100.00%> (ø)

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[asherf]

@mpdavis ping when you have time. not urgent.