MRG: fix many minor documentation nits (#2814) #3910

Job	Run time
coverage	5m 11s
Lints (beta)	43s
test (beta)	2m 19s
Lints (stable)	51s
Check	38s
test (stable)	2m 59s
test_all_features	19m 19s
test (windows)	5m 30s
Check if wasm-pack builds a valid package for the sourmash crate	2m 16s
test (macos)	2m 17s
Check if cbindgen runs cleanly for generating the C headers	1m 36s
minimum_rust_version	6m 43s
Publish (dry-run)	1m 4s
Run tests under wasm32-wasi	2m 3s
	53m 29s

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