Update docs

Author: wojtekmaj

README.md

@@ -110,6 +110,7 @@ Displays an input field complete with custom inputs, native input, and a calenda
 | onCalendarClose      | Function called when the calendar closes.                                                                                                                                                                                                    | n/a                     | `() => alert('Calendar closed')`                                                                               |
 | onCalendarOpen       | Function called when the calendar opens.                                                                                                                                                                                                     | n/a                     | `() => alert('Calendar opened')`                                                                               |
 | onChange             | Function called when the user picks a valid date. If any of the fields were excluded using custom `format`, `new Date(y, 0, 1, 0, 0, 0)`, where `y` is the current year, is going to serve as a "base".                                      | n/a                     | `(value) => alert('New date is: ', value)`                                                                     |
+| onFocus              | Function called when the focuses an input.                                                                                                                                                                                                   | n/a                     | `(event) => alert('Focused input: ', event.target.name)`                                                       |
 | openCalendarOnFocus  | Whether to open the calendar on input focus.                                                                                                                                                                                                 | `true`                  | `false`                                                                                                        |
 | portalContainer      | Element to render the calendar in using portal.                                                                                                                                                                                              | n/a                     | `document.getElementById('my-div')`                                                                            |
 | required             | Whether date input should be required.                                                                                                                                                                                                       | `false`                 | `true`                                                                                                         |