Revise Siren documentation #18934

Job	Run time
target-branch-check	1s
check-code	9m 27s
check-msrv	5m 10s
Check for 'skip-ci' label	1s
lockbud	13m 47s
beacon-chain-tests	14m 40s
release-tests-windows	14m 25s
debug-tests-ubuntu	8m 49s
network-tests	14m 38s
op-pool-tests	14m 38s
release-tests-ubuntu	14m 21s
slasher-tests	1m 37s
state-transition-vectors-ubuntu	2m 22s
basic-simulator-ubuntu	13m 9s
cargo-udeps	7m 27s
cli-check	6m 46s
compile-with-beta-compiler	13m 43s
ef-tests-ubuntu	8m 37s
execution-engine-integration-ubuntu	10m 4s
fallback-simulator-ubuntu	11m 3s
test-suite-success	1s
	3h 4m 46s

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