heading level and doc for masonry readme #2364

Job	Run time
cargo check (msrv) (wasm32)	17s
cargo clippy (windows-latest)	4m 33s
cargo check (msrv) (windows-latest)	2m 6s
cargo check (aarch64-android)	27s
cargo clippy (macos-latest)	2m 33s
cargo check (msrv) (macos-latest)	1m 15s
cargo clippy (wasm32)	2m 5s
cargo clippy (ubuntu-latest)	3m 27s
cargo check (msrv) (ubuntu-latest)	1m 17s
cargo doc	42s
Prime LFS Cache	38s
cargo test (wasm32)	43s
formatting	1m 7s
typos	24s
cargo test (windows-latest)	3m 37s
cargo test (macos-latest)	2m 20s
cargo test (ubuntu-latest)	4m 29s
	32m 0s

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