Fix #198 -- Allow using Django settings for linter configuration

[David-Wobrock]

Fixes #198

[codecov-commenter]

Codecov Report

Merging #199 (7077c70) into main (80b5c1d) will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #199      +/-   ##
==========================================
+ Coverage   93.50%   93.54%   +0.04%     
==========================================
  Files          79       79              
  Lines        1770     1782      +12     
==========================================
+ Hits         1655     1667      +12     
  Misses        115      115              

Impacted Files	Coverage Δ
...ation_linter/management/commands/lintmigrations.py	90.10% <100.00%> (+1.08%)	⬆️
tests/functional/test_lintmigrations_command.py	100.00% <100.00%> (ø)

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