XDG support?

[favonia]

Recent Emacs will also check ~/.config/emacs/init.el and opam user-setup should emulate the main logic used by Emacs. That is, perhaps this function needs to be changed:

opam-user-setup/emacs/emacs.ml

Lines 101 to 108 in 8208197

	let dotemacs =
	let ( / ) = Filename.concat in
	let dotemacs = ".emacs" in
	let dotemacsdinit = ".emacs.d" / "init.el" in
	if not (Sys.file_exists (home/dotemacs)) &&
	Sys.file_exists (home/dotemacsdinit)
	then dotemacsdinit
	else dotemacs

It might also be useful to have an option to specify the location of configuration files that will somehow work with --editors.