Add tests for the indented syntax #1641

Job	Run time
JS API \| Pure JS \| Browser	1m 30s
JS API \| Embedded \| Node lts/* \| ubuntu-latest	4m 50s
JS API \| Embedded \| Node lts/* \| windows-latest	7m 6s
JS API \| Pure JS \| Node lts/* \| ubuntu-latest	1m 23s
JS API \| Embedded \| Node lts/* \| macos-latest	4m 11s
Language \| Dart Sass \| Dart stable	1m 1s
JS API \| Pure JS \| Node lts/* \| windows-latest	3m 48s
Lint spec files	15s
Language \| Dart Sass \| Dart dev	1m 6s
JS API \| Embedded \| Node lts/-1 \| ubuntu-latest	4m 49s
JS API \| Pure JS \| Node lts/* \| macos-latest	1m 18s
JS API \| Embedded \| Node lts/-2 \| ubuntu-latest	5m 2s
JS API \| Pure JS \| Node lts/-1 \| ubuntu-latest	1m 20s
JS API \| Embedded \| Node lts/-3 \| ubuntu-latest	1m 36s
Static analysis	17s
JS API \| Pure JS \| Node lts/-2 \| ubuntu-latest	1m 22s
Unit tests	37s
JS API \| Pure JS \| Node lts/-3 \| ubuntu-latest	1m 28s
	42m 59s

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