Add relative color syntax tests for the color() function (#1993) #1511

Job	Run time
JS API \| Pure JS \| Browser	1m 49s
Language \| Dart Sass \| Dart stable	1m 1s
JS API \| Pure JS \| Node lts/* \| ubuntu-latest	1m 17s
Language \| Dart Sass \| Dart dev	1m 3s
JS API \| Embedded \| Node lts/* \| ubuntu-latest	4m 52s
JS API \| Pure JS \| Node lts/* \| windows-latest	3m 58s
Lint spec files	17s
JS API \| Embedded \| Node lts/* \| windows-latest	8m 34s
JS API \| Pure JS \| Node lts/* \| macos-latest	1m 55s
JS API \| Embedded \| Node lts/* \| macos-latest	4m 22s
JS API \| Pure JS \| Node lts/-1 \| ubuntu-latest	1m 22s
Static analysis	23s
Unit tests	42s
JS API \| Embedded \| Node lts/-1 \| ubuntu-latest	5m 54s
JS API \| Pure JS \| Node lts/-2 \| ubuntu-latest	1m 29s
JS API \| Embedded \| Node lts/-2 \| ubuntu-latest	4m 53s
JS API \| Pure JS \| Node lts/-3 \| ubuntu-latest	1m 32s
JS API \| Embedded \| Node lts/-3 \| ubuntu-latest	1m 37s
	47m 0s

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