chore: ignore CHANGELOG.md from markdownlint #1700

Job	Run time
Lint	47s
Test (20, 9)	1m 18s
Test (lts/*, 9)	1m 12s
Test without ESLint Stylistic	1m 15s
Test (21, 9)	1m 24s
Test (18, 9)	1m 22s
Test (18, 8)	1m 24s
	8m 42s

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