Add Dockerfiles to graderservice and illumidesk folders

[jgwerner]

• Adds Dockerfiles to graderservice and illumidesk folders by copying source files directly using the COPY directive
• Updates contribution guide

Closes #563

[codecov]

Codecov Report

Merging #564 (397e923) into main (e285fcc) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #564   +/-   ##
=======================================
  Coverage   75.59%   75.59%           
=======================================
  Files          15       15           
  Lines        1008     1008           
=======================================
  Hits          762      762           
  Misses        246      246           

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