Revise Siren documentation #18932

Job	Run time
target-branch-check	1s
lockbud	13m 32s
Check for 'skip-ci' label	1s
check-code	9m 5s
check-msrv	5m 2s
beacon-chain-tests	13m 35s
release-tests-windows	13m 19s
network-tests	13m 36s
slasher-tests	1m 35s
release-tests-ubuntu	13m 28s
op-pool-tests	13m 32s
basic-simulator-ubuntu	13m 10s
cargo-udeps	7m 44s
cli-check	6m 22s
debug-tests-ubuntu	10m 5s
compile-with-beta-compiler	13m 31s
ef-tests-ubuntu	10m 56s
execution-engine-integration-ubuntu	10m 19s
fallback-simulator-ubuntu	14m 7s
state-transition-vectors-ubuntu	2m 35s
test-suite-success	1s
	3h 5m 36s

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