Add a macro to make initialization easier #249

Job	Run time
test	55s
check (thumbv7m-none-eabi, nightly)	21s
check (thumbv6m-none-eabi, stable)	21s
check (thumbv6m-none-eabi, nightly)	23s
Clippy	21s
Format	13s
check (thumbv7m-none-eabi, stable)	22s
rustdoc	18s
	3m 14s

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