chore: use const in example #14

Job	Run time
build (windows-latest, main) / build	58s
build (ubuntu-latest, stable) / build	27s
build (windows-2019, stable) / build	1m 30s
build (windows-2022, beta) / build	43s
pana / build	2m 1s
dartdoc / build	26s
	6m 5s

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