Add elisp-demos to lang/emacs-lisp module

This is an extremely useful package which adds little examples to the
help docs for a massive number of elisp functions.

https://github.com/xuchunyang/elisp-demos

modules/lang/emacs-lisp/config.el

@@ -121,6 +121,12 @@ This marks a foldable marker for `outline-minor-mode' in elisp buffers.")
     (add-hook 'flycheck-mode-hook #'flycheck-cask-setup nil t)))
 
 
+(def-package! elisp-demos
+  :commands elisp-demos-advice-helpful-update
+  :init
+  (advice-add 'helpful-update :after #'elisp-demos-advice-helpful-update))
+
+
 ;;
 ;; Project modes