Add tests for underscores where hyphens aren't allowed (#1994) #1510

Job	Run time
JS API \| Pure JS \| Browser	3m 28s
JS API \| Embedded \| Node lts/* \| ubuntu-latest	6m 50s
Language \| Dart Sass \| Dart stable	56s
JS API \| Embedded \| Node lts/* \| windows-latest	6m 49s
JS API \| Pure JS \| Node lts/* \| ubuntu-latest	1m 12s
Language \| Dart Sass \| Dart dev	54s
Lint spec files	15s
JS API \| Embedded \| Node lts/* \| macos-latest	3m 47s
JS API \| Pure JS \| Node lts/* \| windows-latest	4m 48s
JS API \| Pure JS \| Node lts/* \| macos-latest	1m 10s
Static analysis	16s
JS API \| Pure JS \| Node lts/-1 \| ubuntu-latest	3m 25s
Unit tests	39s
JS API \| Embedded \| Node lts/-1 \| ubuntu-latest	4m 47s
JS API \| Pure JS \| Node lts/-2 \| ubuntu-latest	1m 21s
JS API \| Embedded \| Node lts/-2 \| ubuntu-latest	4m 59s
JS API \| Pure JS \| Node lts/-3 \| ubuntu-latest	1m 30s
JS API \| Embedded \| Node lts/-3 \| ubuntu-latest	4m 53s
	51m 59s

Provide feedback