Support MaterialAccentColor

[lcdsmao]

What does this change?

Support generating MaterialAccentColor.
Related: #39

What is the value of this and can you measure success?

CI pass

[codecov]

Codecov Report

Merging #40 into main will increase coverage by 0.29%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #40      +/-   ##
==========================================
+ Coverage   99.25%   99.54%   +0.29%     
==========================================
  Files          16       16              
  Lines         402      439      +37     
==========================================
+ Hits          399      437      +38     
+ Misses          3        2       -1     

Impacted Files	Coverage Δ
lib/src/generators/colors_generator.dart	98.24% <100.00%> (+2.69%)	⬆️
lib/src/utils/color.dart	100.00% <100.00%> (ø)

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