Add optionalProps for <Text> for allowFontScaling={false}

[lc3t35]

from sohobloo/react-native-modal-dropdown#243

On Android, fonts are automatically adjusted, to prevent this you can add allowFontScaling={false} props for .
Current implementation does not include a way to inject such props in Text, adding dropdownTextProps in props would be nice.

const row = !renderRow ?
      (<Text style={[
        styles.rowText,
        dropdownTextStyle,
        highlighted && styles.highlightedRowText,
        highlighted && dropdownTextHighlightStyle
      ]}
      {...dropdownTextProps}
      >
        {rowData}
      </Text>) :