Adds new convenience macros like print! and insert!, and adds classes;
which are helper functions that can be called inline within format!,
print! et co, e.g.
(format! "%s" (filename "/tmp/some/file")) ; => file
(format! "%s" (relpath "/tmp/some/file" "/tmp")) ; => some/file
(format! "%s" (dirname "/tmp/some/file")) ; => /tmp/some
Check out doom-format-class-alist for more.