Add a dockercompose file

[markstory]

Also switch to using .dockerignore instead of more verbose COPY operations

Refs #57

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.03%. Comparing base (1d09911) to head (2ba98a5).
Report is 2 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master      #59      +/-   ##
============================================
- Coverage     92.07%   92.03%   -0.04%     
  Complexity      864      864              
============================================
  Files           170      170              
  Lines          8602     8602              
============================================
- Hits           7920     7917       -3     
- Misses          682      685       +3     

Flag	Coverage Δ
flutter	90.52% <ø> (-0.08%)	⬇️
phpunit	93.34% <ø> (ø)

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