Fills missing documentation and adds warn(missing_docs) #509

Job	Run time
clippy/stable	21s
Pass MSRV values to other jobs	3s
format/nightly	13s
nostd/thumbv6m-none-eabi/stable	21s
cargo-careful	2m 18s
cross_test/s390x-unknown-linux-gnu/stable	8m 5s
docs/nightly	22s
miri	10m 47s
cross_test/i686-unknown-linux-gnu/stable	2m 0s
blas-msrv	58s
tests/stable	2m 31s
tests/beta	2m 29s
tests/nightly	2m 52s
tests/1.64.0	3m 8s
conclusion	2s
	36m 30s

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