CI: Dependabot for actions. #251

Job	Run time
no_std	32s
miri	1m 18s
build (ubuntu, stable, locked, true)	11m 32s
build (windows, stable, locked, false)	14m 41s
build (macos, stable, locked, false)	15m 20s
build (ubuntu, nightly, locked, false)	11m 11s
build (ubuntu, beta, locked, false)	11m 49s
build (ubuntu, stable, latest, false)	12m 13s
build (ubuntu, stable, minimal, false)	11m 56s
features	23m 17s
deploy	4s
fuzz	15m 36s
	2h 9m 29s

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