Document feature flags #1205

Job	Run time
License check	1m 37s
Cancel Previous Runs	3s
cargo build --release --workspace --locked --exclude test-no-std	1m 54s
cargo build --release -p test-no-std --features api-client	1m 4s
cargo build --release -p test-no-std --features compose-macros	1m 4s
cargo build --release -p test-no-std --features node-api	1m 9s
cargo build --release -p test-no-std --features primitives	53s
cargo build --target wasm32-unknown-unknown --no-default-features --features sync-api	58s
cargo build --no-default-features --features "std jsonrpsee-client"	1m 18s
cargo clippy --workspace --exclude test-no-std -- -D warnings	1m 0s
cargo clippy --all-features --examples -- -D warnings	41s
cargo test --release --workspace --all-features --exclude test-no-std	2m 7s
cargo fmt --all -- --check	40s
Taplo fmt	10s
examples	1s
	14m 39s

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