Merge pull request #30 from ex7r3me/onPressClose_docs

Add onPressClose to README

README.md

@@ -33,6 +33,7 @@ import { Picker } from 'emoji-mart-native'
 | **onClick** | | | Params: `(emoji, event) => {}`. Not called when emoji is selected with `enter` |
 | **onSelect** | | | Params: `(emoji) => {}`  |
 | **onSkinChange** | | | Params: `(skin) => {}` |
+| **onPressClose** | | | Trigger when user press back button
 | **perLine** | | `9` | Number of emojis per line. While there’s no minimum or maximum, this will affect the picker’s width. This will set *Frequently Used* length as well (`perLine * 4`) |
 | **i18n** | | [`{…}`](#i18n) | [An object](#i18n) containing localized strings |
 | **native** | | `false` | Renders the native unicode emoji |