Add documentation

[tsalo]

Closes none.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 26.21%. Comparing base (fb966c3) to head (add8bd1).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/fmripost_template/workflows/base.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main       #8   +/-   ##
=======================================
  Coverage   26.21%   26.21%           
=======================================
  Files          17       17           
  Lines        1358     1358           
  Branches      202      202           
=======================================
  Hits          356      356           
  Misses        992      992           
  Partials       10       10           

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