Adds styles on operation keys
Adds styles on operation keys

benoitvallon/react-native-nw-react-calculator,srgpqt/react-native-nw-react-calculator,srgpqt/react-native-nw-react-calculator,benoitvallon/react-native-nw-react-calculator,benoitvallon/react-native-nw-react-calculator,srgpqt/react-native-nw-react-calculator