~/.emacs.d: Add shortcut for writing diary entries

`C-x C-d` opens a buffer with the contents of `~/w/YYYY-mm-dd.txt` with
the simple-writing-mode enabled.  Very handy.

.emacs.d/init.el

(global-set-key (kbd "C-x C-S-n") 'create-note)
(defun find-diary-entry ()
  (interactive)
  (find-file (format-time-string "~/w/%Y-%m-%d.txt"))
  (simple-writing-mode t))
(global-set-key (kbd "C-x C-d") 'find-diary-entry)
(custom-set-faces
 '(default ((t (:family "Fantasque Sans Mono" :height 124)))))