Auto merge of #14358 - chenpighead:webkit-text-stroke, r=canaltinova

stylo - implement -webkit-text-fill-color and -webkit-text-stroke.

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Implement -webkit-text-fill-color property.
Implement -webkit-text-stroke property, along with -webkit-text-stroke-width and -webkit-text-stroke-color longhand properties.

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #13849 (github issue number if applicable).

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