cpufeatures: add mentions of `avx512vbmi` and `avx512vbmi2` to readme… #205

Job	Run time
build (1.65.0, armv7a-none-eabi)	2m 59s
build (1.65.0, thumbv7em-none-eabi)	2m 21s
build (1.65.0, wasm32-unknown-unknown)	2m 19s
build (stable, armv7a-none-eabi)	25s
build (stable, thumbv7em-none-eabi)	18s
build (stable, wasm32-unknown-unknown)	28s
test (1.65.0)	2m 46s
test (stable)	20s
minimal-versions / minimal-versions	26s
	12m 22s

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