Improve config validation #471

Job	Run time
JS Tests (16.x)	2m 20s
Lint (18.x)	28s
JS Tests (18.x)	2m 13s
Build and run integration tests (18.x)	2m 46s
Lint (19.x)	31s
JS Tests (19.x)	2m 24s
Lint (20.x)	27s
Build and run integration tests (19.x)	2m 48s
JS Tests (20.x)	2m 8s
Lint (21.x)	36s
Build and run integration tests (20.x)	2m 37s
JS Tests (21.x)	2m 8s
Build and run integration tests (21.x)	2m 42s
Publish to NPM	32s
	24m 40s

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