feat(image-list): Add corner radius mixin

[kfranqueiro]

Resolves #2375.

[codecov-io]

Codecov Report

Merging #2385 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2385      +/-   ##
==========================================
- Coverage   98.86%   98.85%   -0.01%     
==========================================
  Files         100      100              
  Lines        4123     4118       -5     
  Branches      528      527       -1     
==========================================
- Hits         4076     4071       -5     
  Misses         47       47

Impacted Files	Coverage Δ
packages/mdc-checkbox/foundation.js	97.47% <0%> (-0.11%)	⬇️
packages/mdc-checkbox/constants.js	100% <0%> (ø)	⬆️

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