Delete trailing whitespace, globally, by default

Also adds doom|disable-delete-trailing-whitespace hook, which can be
used to disable this behavior on a per-buffer basis. If you want to turn
off this global behavior:

  (remove-hook 'write-file-functions #'delete-trailing-whitespace)

modules/lang/emacs-lisp/config.el

@@ -50,7 +50,7 @@
 
   (add-hook! 'emacs-lisp-mode-hook
     #'(;; 3rd-party functionality
-       auto-compile-on-save-mode doom|enable-delete-trailing-whitespace
+       auto-compile-on-save-mode
        ;; fontification
        rainbow-delimiters-mode highlight-quoted-mode
        ;; initialization