[libcxx-commits] [libcxx] [libc++] Document how __tree is layed out and how we iterate through it (PR #152453)

[Louis Dionne via libcxx-commits]

https://github.com/ldionne approved this pull request.

Thanks for the documentation, LGTM with minor tweaks!

https://github.com/llvm/llvm-project/pull/152453