Merge the PM2 model of algae into the main branch

[yalinli2]

Hi @GaYeongKim, thanks so much for the work, as I mentioned in the group meeting, it'll be great to have the _pm2 module in the algae branch into QSDsan's main branch, so I'm opening this PR now :)

I talked with @joyxyz1994 at yesterday's QSDsan office hour and she let me know that the _newpm2 is outdated, so I removed it (18bf33b172ad73c8f049967c08e76e3e6346564e and 61003737d0face944ecbf86d5f75885c41c47245), I also fixed a minor bug in the doc related to the output (b295a8d7769b645fffb97fe8f166022133d6e72e).

Can you take a look and approve it if it looks good to you? I'll merge it in if it has a decent test coverage through the doctest, otherwise I might hold until we have the EcoRecover system in EXPOsan so we'll have better test coverage. Thanks!

[codecov[bot]]

Codecov Report

Merging #92 (e70c518) into main (801564f) will decrease coverage by 0.33%. The diff coverage is 42.20%.

@@            Coverage Diff             @@
##             main      #92      +/-   ##
==========================================
- Coverage   75.26%   74.93%   -0.34%     
==========================================
  Files          85       86       +1     
  Lines       14577    14795     +218     
  Branches     1596     1604       +8     
==========================================
+ Hits        10971    11086     +115     
- Misses       3147     3256     +109     
+ Partials      459      453       -6     

Flag	Coverage Δ
unittests	74.93% <42.20%> (-0.34%)	:arrow_down:

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

Impacted Files	Coverage Δ
qsdsan/processes/_pm2.py	41.93% <41.93%> (ø)
qsdsan/processes/__init__.py	100.00% <100.00%> (ø)
qsdsan/_process.py	67.18% <0.00%> (+1.38%)	:arrow_up:
qsdsan/utils/cod.py	70.54% <0.00%> (+2.73%)	:arrow_up:
qsdsan/_component.py	92.10% <0.00%> (+2.89%)	:arrow_up:

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.