Complete docstrings

[marjanalbooyeh]

The goal of this PR is to complete all the docstring required for readthedocs.

Note: I added a new githook to our pre-commit config that makes sure docstrings follow the numpy format. It could be a little annoying sometimes with too many errors but I think it's helpful for now, just to make sure we're not missing any docstring.

[codecov]

Codecov Report

Merging #50 (102018d) into main (5c47cc4) will increase coverage by 0.00%.
The diff coverage is 100.00%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #50   +/-   ##
=======================================
  Coverage   93.63%   93.63%           
=======================================
  Files          18       18           
  Lines        1382     1383    +1     
=======================================
+ Hits         1294     1295    +1     
  Misses         88       88           

Files	Coverage Δ
hoomd_organics/__init__.py	100.00% <ø> (ø)
hoomd_organics/base/__init__.py	100.00% <ø> (ø)
hoomd_organics/base/molecule.py	96.62% <100.00%> (ø)
hoomd_organics/base/simulation.py	91.26% <ø> (ø)
hoomd_organics/base/system.py	89.49% <100.00%> (ø)
hoomd_organics/library/__init__.py	100.00% <ø> (ø)
hoomd_organics/library/forcefields.py	100.00% <ø> (ø)
hoomd_organics/library/polymers.py	97.33% <ø> (ø)
hoomd_organics/library/simulations/tensile.py	100.00% <100.00%> (ø)
hoomd_organics/modules/__init__.py	100.00% <ø> (ø)
... and 3 more

[chrisjonesBSU]

This is an awesome start! I left a few suggestions. I'll keep checking back to review, and add in some of my own.