Add dependabot.yml for dependency version updates #5729

Job	Run time
fmt	18s
cackle	1m 34s
cargo-deny (advisories)	2m 50s
build (gcc, current)	18m 0s
cargo-deny (bans licenses sources)	47s
rust-check-git-rev-deps	31s
build (gcc, current, --check-test-tx-meta)	16m 54s
build (gcc, next)	5m 14s
build (gcc, next, --check-test-tx-meta)	57m 18s
build (clang, current)	18m 34s
build (clang, current, --check-test-tx-meta)	10m 31s
build (clang, next)	18m 50s
build (clang, next, --check-test-tx-meta)	11m 15s
complete	1s
	2h 42m 37s

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