Added screen-height-width.md

Author: Unicar

react-native/screen-height-width.md

@@ -0,0 +1,12 @@
+To access a screen height and width in `React Native`, import `Dimension`.
+
+Code:
+```React
+
+import { Dimensions } from 'react-native'
+
+const SCREEN_WIDTH = Dimensions.get('window').width
+const SCREEN_HEIGHT = Dimensions.get('window').height
+
+```
+