Add doc comment to `Quat::is_nan` (#565) #1442

Job	Run time
Test (ubuntu-latest, stable)	2m 51s
Test (ubuntu-latest, beta)	2m 59s
Check MSRV (ubuntu-latest, 1.68.2)	58s
Lint	2m 13s
Test (ubuntu-latest, nightly)	2m 44s
Check MSRV (macos-latest, 1.68.2)	57s
Test portable simd (ubuntu-latest, nightly)	39s
Test (macos-latest, stable)	3m 37s
Check MSRV (windows-latest, 1.68.2)	1m 26s
Test portable simd (macos-latest, nightly)	41s
Test (macos-latest, beta)	2m 25s
Test portable simd (windows-latest, nightly)	1m 35s
Test (macos-latest, nightly)	2m 52s
Test (windows-latest, stable)	6m 13s
Test wasm (stable, ubuntu-latest)	4m 46s
Test (windows-latest, beta)	5m 1s
Test (windows-latest, nightly)	5m 13s
	47m 10s

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