Update README structure / content (#410) #750

Job	Run time
formatting	20s
cargo clippy (wasm32)	1m 27s
cargo clippy (windows-latest)	1m 48s
cargo test (windows-latest)	1m 0s
cargo clippy (macos-latest)	1m 10s
cargo test (macos-latest)	33s
cargo clippy (ubuntu-latest)	1m 16s
cargo check (msrv) (windows-latest)	2m 39s
cargo test (ubuntu-latest)	37s
cargo check (msrv) (wasm32)	1m 52s
cargo check (msrv) (macos-latest)	2m 0s
cargo doc	22s
cargo check (msrv) (ubuntu-latest)	1m 52s
typos	4s
cargo test (wasm32)	36s
	17m 36s

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