Add `asm` feature (#10) #95

Job	Run time
Current MSRV is 1.60.0	2m 9s
Build on no_std target (thumbv7em-none-eabi)	25s
clippy	22s
rustfmt	7s
Test on Rust stable (powerpc-unknown-linux-gnu, sudo apt update && sudo apt install gcc-multilib)	24s
Test on Rust stable (x86_64-unknown-linux-gnu)	34s
	4m 1s

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