prelude/python: add docs for PythonLibraryInfo #7580

Job	Run time
Get the latest prelude hash	3s
build (ubuntu-22.04, aarch64-unknown-linux-gnu, true)	9m 7s
build (ubuntu-22.04, aarch64-unknown-linux-musl, true)	9m 12s
build (ubuntu-22.04, x86_64-unknown-linux-gnu)	8m 33s
build (ubuntu-22.04, x86_64-unknown-linux-musl, true)	10m 6s
build (macos-13, aarch64-apple-darwin, true)	19m 26s
build (macos-13, x86_64-apple-darwin)	27m 7s
build (windows-2022, x86_64-pc-windows-msvc, true)	19m 40s
Release `latest` tag	31s
Check if there's a release for this half of the month already	4s
Publish buck2.build	2m 36s
Release bi-monthly tag	0s
	1h 46m 25s

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