Gatsby theme

[mimiflynn]

Replace Gatsby stand alone files with centrally managed theme.

[psmulovics]

@mimiflynn , quick reminder to move the certified image to the content folder instead of deleting (and updating the README.MD to point to the moved image)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.65%. Comparing base (82a5634) to head (c616607).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #890      +/-   ##
==========================================
- Coverage   67.66%   67.65%   -0.02%     
==========================================
  Files         300      300              
  Lines        8982     8982              
  Branches     1028      973      -55     
==========================================
- Hits         6078     6077       -1     
  Misses       2689     2689              
- Partials      215      216       +1     

see 3 files with indirect coverage changes