Add non-standard extension tokens DDD and MMM (localized)

config.js

@@ -26,6 +26,10 @@
  *                 sss    millisecond 000-999 (456)
  *                 T      literal 'T'
  *
+ *               Non-standard extension tokens (localized via i18n):
+ *                 DDD    weekday short name    (Mon., Tue., ...)
+ *                 MMM    month short name      (January, February, ...)
+ *
  *               Date-only forms:  YYYY,  YYYY-MM,  YYYY-MM-DD
  *               Date-time forms:   above + T + HH:mm,  HH:mm:ss,  HH:mm:ss.sss
  *               Any other character is a literal (incl. spaces, tabs, \n).