Update README.md

Author: g1eb

README.md

@@ -59,6 +59,7 @@ angular.module('myApp', [
 | on-change-start | Handler function that is fired on change of start datetime object | none | no |
 | on-change-end | Handler function that is fired on change of end datetime object | none | no |
 | on-close | Handler function that is fired on close of the edit popover | none | no |
+| close-text | Close text shown in the button used to close edit popover | Close | no |
 
 ## Presets