Create a spacemacs layer for the elisp

[alanz]

Originally https://github.com/alanz/HaRe/issues/28

This is only really practical once the elisp is on MELPA, I suspect.

Unless the haskell-mode integration does this automatically

[mrkgnao]

@alanz I think it's more practical to integrate it into the existing Haskell layer, though, as I mention in the referenced issue (syl20bnr/spacemacs#8664) Intero/Stack compatibility is something to think about.