docs: update README #221

Job	Run time
check no-default-features	15s
clippy	1m 21s
check serde	28s
check std	16s
docs	1m 12s
fmt	13s
test stable --no-default-features	2m 27s
Test Native Tokens	1m 44s
test stable	2m 18s
test no_std	29s
test stable --all-features	2m 32s
test beta --no-default-features	2m 22s
test beta	2m 36s
test beta --all-features	2m 31s
test nightly --no-default-features	2m 1s
test nightly	2m 13s
test nightly --all-features	2m 15s
	27m 13s

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