Revise Siren documentation #18931

Job	Run time
lockbud	2m 21s
target-branch-check	1s
Check for 'skip-ci' label	1s
check-code	2m 31s
check-msrv	2m 31s
op-pool-tests	2m 24s
network-tests	2m 24s
beacon-chain-tests	2m 26s
debug-tests-ubuntu	2m 27s
release-tests-ubuntu	2m 25s
release-tests-windows	2m 22s
slasher-tests	1m 44s
basic-simulator-ubuntu	2m 24s
cargo-udeps	2m 23s
cli-check	2m 23s
compile-with-beta-compiler	2m 23s
ef-tests-ubuntu	2m 24s
fallback-simulator-ubuntu	2m 35s
execution-engine-integration-ubuntu	2m 25s
state-transition-vectors-ubuntu	2m 21s
test-suite-success	1s
	42m 56s

Provide feedback