Document unit_of and value_of functions #337

Job	Run time
Ensure 'cargo fmt' has been run	18s
Extract crate metadata	7s
Documentation checks	8m 40s
Minimum supported rust version	2m 16s
aarch64-unknown-linux-gnu (ubuntu-20.04)	3m 39s
arm-unknown-linux-gnueabihf (ubuntu-20.04)	4m 43s
arm-unknown-linux-musleabihf (ubuntu-20.04)	4m 26s
i686-pc-windows-msvc (windows-2019)	7m 42s
i686-unknown-linux-gnu (ubuntu-20.04)	4m 22s
i686-unknown-linux-musl (ubuntu-20.04)	5m 17s
x86_64-apple-darwin (macos-12)	5m 41s
x86_64-pc-windows-msvc (windows-2019)	5m 24s
x86_64-unknown-linux-gnu (ubuntu-20.04)	3m 33s
x86_64-unknown-linux-musl (ubuntu-20.04)	4m 50s
	1h 0m 58s

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