docs(workflow): adds a description at the top of each file #402

Job	Run time
Generate crates matrix	12s
Check crates matrix	2s
Build tower-batch-control crate	33s
Build tower-fallback crate	17s
Build zebra-chain crate	2m 0s
Build zebra-consensus crate	7m 31s
Build zebra-network crate	2m 10s
Build zebra-node-services crate	1m 47s
Build zebra-rpc crate	7m 53s
Build zebra-scan crate	6m 15s
Build zebra-script crate	1m 41s
Build zebra-state crate	7m 7s
Build zebra-test crate	41s
Build zebra-utils crate	8m 9s
Build zebrad crate	11m 31s
Open or update issues for building crates individually failures	0s
	57m 49s

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