ENH: add rich transient progress spinner

[neutrinoceros]

need to figure out if this is worth adding rich as a mandatory dependency (probably not, but it's fun though).

TODO:

• edit changelog
• edit README (stop boasting about not having dependencies in Python 3.10)

[codecov]

Codecov Report

Merging #124 (163d73a) into main (191bab4) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #124   +/-   ##
=======================================
  Coverage   99.20%   99.20%           
=======================================
  Files          10       10           
  Lines         375      377    +2     
=======================================
+ Hits          372      374    +2     
  Misses          3        3           

Flag	Coverage Δ
unittests	99.20% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
wxc/cli.py	97.01% <100.00%> (+0.09%)	⬆️

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