Revise Siren documentation #18945

Job	Run time
Check for 'skip-ci' label	1s
check-code	9m 16s
lockbud	13m 17s
check-msrv	5m 5s
target-branch-check	1s
release-tests-ubuntu	20m 26s
release-tests-windows	45m 36s
beacon-chain-tests	21m 29s
op-pool-tests	15m 51s
network-tests	18m 12s
basic-simulator-ubuntu	13m 6s
debug-tests-ubuntu	5m 27s
ef-tests-ubuntu	8m 14s
slasher-tests	1m 34s
fallback-simulator-ubuntu	10m 52s
state-transition-vectors-ubuntu	2m 33s
cargo-udeps	7m 26s
cli-check	6m 29s
compile-with-beta-compiler	13m 45s
execution-engine-integration-ubuntu	13m 4s
test-suite-success	5s
	3h 51m 49s

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