add shift-arrow info to the readme

README.md

@@ -29,7 +29,7 @@ cursewords todaysnyt.puz
 
 ## Usage
 
-If you've used a program to solve crossword puzzles, navigation should be pretty intuitive. `tab` and `shift+tab` are the workhorses for navigation between blanks. `page up` and `page down` (on Mac, `Fn+` up/down arrow keys) jump between words without considering blank spaces. `ctrl+g`, followed by a number, will jump directly to the space with that number.
+If you've used a program to solve crossword puzzles, navigation should be pretty intuitive. `tab` and `shift+tab` are the workhorses for navigation between blanks. Arrow keys will navigate the grid according to the direction of the cursor, and `shift+arrow` will move through words perpendicular to the cursor. `page up` and `page down` (on Mac, `Fn+` up/down arrow keys) jump between words without considering blank spaces. `ctrl+g`, followed by a number, will jump directly to the space with that number.
 
 If you need some help, `ctrl+c` will check the current square, word, or entire puzzle for errors, and `ctrl+r` will reveal answers (subject to the same scoping options). To clear all entries on the puzzle, use `ctrl+x`, and to reset the puzzle to its original state (resetting the timer and removing any stored information about hints and corrections), use `ctrl+z`.