Sorry, I was unclear; by "core" I mean "the Emacs distribution itself", as opposed to libraries you find on Github, EmacsWiki, or wherever else that isn't part

Sorry, I was unclear; by "core" I mean "the Emacs distribution itself", as opposed to libraries you find on Github, EmacsWiki, or wherever else that isn't part of the standard Lisp library you get when you download the Emacs tarball.