docs(readme): update new option in README.md

README.md

@@ -52,6 +52,7 @@ use {
 theme = 'hyper' --  theme is doom and hyper default is hyper
 disable_move    --  default is false disable move keymap for hyper
 shortcut_type   --  shorcut type 'letter' or 'number'
+shuffle_letter  --  default is true, shortcut 'letter' will be randomize, set to false to have ordered letter.
 change_to_vcs_root -- default is false,for open file in hyper mru. it will change to the root of vcs
 config = {},    --  config used for theme
 hide = {