chore: add compile time flags to disable rayon (#240) #306

Job	Run time
Build - x86_64-unknown-linux-gnu	1m 7s
Build - aarch64-unknown-linux-gnu	1m 11s
Build - aarch64-apple-darwin	1m 6s
Build - x86_64-apple-darwin	1m 22s
Build - x86_64-pc-windows-gnu	3m 49s
Test - x86_64-unknown-linux-gnu	47s
Test - aarch64-unknown-linux-gnu	1m 35s
Test - x86_64-apple-darwin	1m 10s
Test - aarch64-apple-darwin	49s
Test - x86_64-pc-windows-gnu	1m 34s
Publish	0s
	14m 30s

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