Creation docstrings

[OliviaLynn]

Problem & Solution Description (including issue #)

For LSSTDESC/rail#22 (creation docstrings only)

Made this branch before seeing Drew's dedicated branch for the issue, sorry Drew

Code Quality

• My code follows the code style of this project
• My code contains relevant comments and necessary documentation for future maintainers; the change is reflected in applicable demos/tutorials (with output cleared!) and added/updated docstrings use the NumPy docstring format

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (263b2a6) 96.96% compared to head (8cfc16f) 97.17%.
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #78      +/-   ##
==========================================
+ Coverage   96.96%   97.17%   +0.21%     
==========================================
  Files          32       32              
  Lines        1714     1736      +22     
==========================================
+ Hits         1662     1687      +25     
+ Misses         52       49       -3     

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[drewoldag]

This looks great. Thank you so much for cleaning this up :)