ci: add minimum GitHub token permissions for workflows #9

Job	Run time
build (12.x, ubuntu-latest, bash)	25s
build (12.x, macos-latest, bash)	49s
build (12.x, windows-latest, bash)	51s
build (12.x, windows-latest, powershell)	44s
build (14.x, ubuntu-latest, bash)	14s
build (14.x, macos-latest, bash)	31s
build (14.x, windows-latest, bash)	57s
build (14.x, windows-latest, powershell)	55s
build (16.x, ubuntu-latest, bash)	24s
build (16.x, macos-latest, bash)	25s
build (16.x, windows-latest, bash)	49s
build (16.x, windows-latest, powershell)	43s
build (17.x, ubuntu-latest, bash)	18s
build (17.x, macos-latest, bash)	43s
build (17.x, windows-latest, bash)	47s
build (17.x, windows-latest, powershell)	1m 34s
	11m 9s

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