[book] Update book with ZSA changes #549

Job	Run time
Test on ubuntu-latest	11m 30s
Bitrot check	1m 26s
Build target wasm32-unknown-unknown	2m 53s
Book tests	2m 23s
Build target wasm32-wasi	2m 40s
Test on windows-latest	15m 40s
Test on i686-unknown-linux-gnu	23m 27s
Test on macOS-latest	10m 30s
Test on i686-unknown-linux-gnu with beta features	23m 38s
Test on ubuntu-latest with beta features	11m 18s
Code coverage	3h 0m 59s
Test on windows-latest with beta features	15m 22s
Intra-doc links	2m 24s
Test on i686-unknown-linux-gnu with nightly features	24m 2s
Rustfmt	17s
Test on macOS-latest with beta features	10m 29s
Test on ubuntu-latest with nightly features	11m 37s
Test on windows-latest with nightly features	16m 21s
Test on macOS-latest with nightly features	10m 39s
	6h 17m 35s

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