chore: release 0.4.0 #2

Job	Run time
clippy	46s
cfg-check	43s
docs	42s
doctest	1m 12s
feature-checks	44s
fmt	11s
no-std	16s
test stable --no-default-features	1m 7s
test stable	1m 9s
test stable --all-features	1m 7s
test nightly --no-default-features	1m 8s
test nightly	1m 3s
test nightly --all-features	1m 8s
test 1.79 --no-default-features	1m 9s
test 1.79	1m 4s
	13m 29s

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