Fixed typo.'

Author: jcs090218

README.md

@@ -4,7 +4,7 @@
 # better-scroll
 > Improve user experience when scrolling window.
 
-Normally scroll up/down will move the cursor to the window boundry corresponding to
+Normally scroll up/down will move the cursor to the window boundary corresponding to
 the direction on how the window scrolls. This package provides it's own scrolling
 functions that will preserve cursor's position.