Add README.md to umbrella #14012

Job	Run time
isdraft / isdraft	1s
preflight / preflight	44s
preflight / ci-versions	1m 6s
cargo-check-benches (master)	19m 29s
cargo-check-all-crate-macos	11m 13s
cargo-check-benches (current)	21m 37s
test-frame-ui	25m 37s
cargo-check-each-crate (1)	14m 46s
cargo-check-each-crate (2)	17m 50s
test-full-crypto-feature	2m 29s
cargo-check-each-crate (3)	6m 13s
test-node-metrics	7m 54s
cargo-check-each-crate (4)	14m 36s
cargo-check-each-crate (5)	20m 53s
cargo-check-each-crate (6)	12m 28s
cargo-check-each-crate (7)	24m 12s
test-frame-examples-compile-to-wasm	2m 47s
test-deterministic-wasm	5m 50s
check-tracing	2m 4s
check-metadata-hash	5m 44s
node-bench-regression-guard	13s
All test misc tests passed	1s
	3h 37m 47s

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