[libc-commits] [libc] [libc][docs] start documenting c23 support (PR #81933)

[The Phantom Derpstorm via libc-commits]

ThePhD wrote:

Yes, this was an oversight in the c23 working draft everyone is using. A better version is here: https://drive.google.com/file/d/12kNvH0aYJhe3ZPmBKH_Nk5maTfxH2lJv/view

https://github.com/llvm/llvm-project/pull/81933