New plugin: LCH color space

[omgovich]

Adding support for LCH color model: https://lea.verou.me/2020/04/lch-colors-in-css-what-why-and-how/

[codecov-commenter]

Codecov Report

Merging #31 (58928f0) into master (2dbdd81) will not change coverage. The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master       #31   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           27        30    +3     
  Lines          336       372   +36     
  Branches        73        79    +6     
=========================================
+ Hits           336       372   +36     

Impacted Files	Coverage Δ
src/index.ts	100.00% <ø> (ø)
src/colorModels/hslString.ts	100.00% <100.00%> (ø)
src/colorModels/lch.ts	100.00% <100.00%> (ø)
src/colorModels/lchString.ts	100.00% <100.00%> (ø)
src/plugins/lch.ts	100.00% <100.00%> (ø)

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[github-actions[bot]]

Size Change: +1.13 kB (+20%) 🚨

Total Size: 6.84 kB

Filename	Size	Change
./dist/index.js	1.73 kB	-6 B (0%)
./dist/plugins/lch.js	1.14 kB	+1.14 kB (new file)	🆕

ℹ️ View Unchanged

| Filename | Size | Change | | :--- | :---: | :---: | | `./dist/plugins/a11y.js` | 456 B | 0 B | | `./dist/plugins/hwb.js` | 613 B | 0 B | | `./dist/plugins/lab.js` | 875 B | 0 B | | `./dist/plugins/names.js` | 1.36 kB | 0 B | | `./dist/plugins/xyz.js` | 668 B | 0 B |

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