Add npe2 list command to discover/display all currently installed plugins

[tlambert03]

work in progress, but here's the idea:

[codecov]

Codecov Report

Merging #192 (1325ac0) into main (aba218b) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main      #192   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           30        30           
  Lines         2101      2178   +77     
=========================================
+ Hits          2101      2178   +77     

Impacted Files	Coverage Δ
npe2/cli.py	100.00% <100.00%> (ø)

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[nclack]

I find myself using this constantly fwiw. will need rich in the install_requires?

[tlambert03]

I find myself using this constantly fwiw.

what do you mean? Like, you check out this branch and run it? 😂 if so we need to get this in for you :)

will need rich in the install_requires?

Yep, will do thanks.

[tlambert03]

Ok, need to add tests and more docs, but i think the implementation is roughly where I'd have it, so marking ready for first review. I added an optional --format flag.

[tlambert03]

I've merged in #197 here, so that should be reviewed first. I also added docs and cleaned this up a bit. So the only thing left now is to complete test coverge

[nclack]

Thanks. Looks great.