[change] TextInput 'onKeyPress' includes modifier keys

Include modifier keys in the 'nativeEvent'. This allows keyboard
shortcuts such as "Shift+Enter" to be implemented for submiting text
input content when the modality is keyboard + mouse rather than touch.

docs/components/TextInput.md

@@ -106,7 +106,8 @@ Callback that is called when the text input is focused.
 Callback that is called when a key is pressed. This will be called with `{
 nativeEvent: { key: keyValue } }` where keyValue is 'Enter` or 'Backspace' for
 respective keys and the typed-in character otherwise including ' ' for space.
-Fires before onChange callbacks.
+Modifier keys are also included in the nativeEvent. Fires before onChange
+callbacks.
 
 **onSelectionChange**: ?function