feat: add devguide #196

Job	Run time
Code Coverage	9m 29s
clippy	54s
docs	29s
feature-checks	16s
fmt	14s
test stable --no-default-features	1m 23s
test stable	1m 26s
test stable --all-features	1m 26s
test beta --no-default-features	1m 28s
test beta	1m 28s
test beta --all-features	1m 25s
test nightly --no-default-features	2m 48s
test nightly	2m 52s
test nightly --all-features	2m 50s
	28m 28s

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