Create dependabot.yml #1644

Job	Run time
check	3m 45s
rustfmt	12s
audit	9s
clippy	4m 12s
test	9m 50s
integration-test-five-nodes	13m 50s
cross-aarch64	1m 47s
cross-armv7	2m 40s
integration-test-debts	17m 1s
integration-test-eth-payments	13m 38s
integration-test-althea-payment	17m 5s
integration-test-db-migration	12m 8s
integration-test-multi-exit	12m 29s
integration-test-validate-contract	12m 11s
	2h 0m 57s

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