Doc: Add use case, RobustMQ #4087

Job	Run time
lint	12m 11s
cluster-benchmark (cluster_benchmark)	50s
openraft-feature-test (nightly)	50s
examples (stable, memstore)	37s
openraft-feature-test (nightly, serde)	52s
examples (stable, raft-kv-memstore)	2m 33s
openraft-test (stable, 0)	3m 29s
openraft-feature-test (nightly, single-term-leader)	49s
openraft-test-bench (nightly)	59s
examples (stable, raft-kv-memstore-network-v2)	48s
openraft-test (nightly, 30)	3m 26s
openraft-feature-test (nightly, single-term-leader,serde,singlethreaded)	56s
examples (stable, raft-kv-memstore-opendal-snapshot-data)	1m 1s
openraft-test (nightly, 0, single-term-leader)	3m 40s
examples (stable, raft-kv-memstore-singlethreaded)	50s
rt-monoio	43s
examples (stable, raft-kv-rocksdb)	8m 13s
stores (stores/memstore)	52s
examples (nightly, memstore)	56s
stores (stores/rocksstore)	6m 32s
Build (nightly, bench,serde,bt,singlethreaded)	49s
examples (nightly, raft-kv-memstore)	2m 18s
stores (stores/sledstore)	1m 3s
tests-feature-test (nightly)	3m 1s
examples (nightly, raft-kv-memstore-network-v2)	1m 8s
tests-feature-test (nightly, single-term-leader)	2m 59s
examples (nightly, raft-kv-memstore-opendal-snapshot-data)	1m 24s
tests-feature-test (nightly, loosen-follower-log-revert)	3m 1s
examples (nightly, raft-kv-memstore-singlethreaded)	1m 7s
examples (nightly, raft-kv-rocksdb)	6m 45s
	1h 14m 42s

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