Add pyGeo specific contribution information

[hajdik]

Purpose

Add a link from the pyGeo docs to the general MACH contribution guide page as well as pyGeo specific information

Expected time until merged

1 day, very simple addition

Type of change

• [ ] Bugfix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (non-backwards-compatible fix or feature)
• [ ] Code style update (formatting, renaming)
• [ ] Refactoring (no functional changes, no API changes)
• [X] Documentation update
• [ ] Maintenance update
• [ ] Other (please describe)

Checklist

• [ ] I have run flake8 and black to make sure the Python code adheres to PEP-8 and is consistently formatted
• [ ] I have formatted the Fortran code with fprettify or C/C++ code with clang-format as applicable
• [ ] I have run unit and regression tests which pass locally with my changes
• [ ] I have added new tests that prove my fix is effective or that my feature works
• [ ] I have added necessary documentation

[codecov[bot]]

Codecov Report

Merging #161 (6ba70d4) into main (022e6b2) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #161   +/-   ##
=======================================
  Coverage   63.93%   63.93%           
=======================================
  Files          47       47           
  Lines       11819    11819           
=======================================
  Hits         7556     7556           
  Misses       4263     4263           

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[ArshSaja]

approved