merge method
Implementation
ButtonConfig merge(ButtonConfig? other) {
if (other == null) return this;
return copyWith(
bigButtonRadius: other._bigButtonRadius,
bigButtonHeight: other._bigButtonHeight,
bigButtonFontSize: other._bigButtonFontSize,
smallButtonRadius: other._smallButtonRadius,
smallButtonHeight: other._smallButtonHeight,
smallButtonFontSize: other._smallButtonFontSize,
);
}