merge method
Implementation
ZeroNavigationDrawerStyle merge(ZeroNavigationDrawerStyle? other) {
if (other == null) return this;
return copyWith(
backgroundColor: other.backgroundColor,
headerTitleStyle: headerTitleStyle?.merge(other.headerTitleStyle) ??
other.headerTitleStyle,
sectionTitleStyle: sectionTitleStyle?.merge(other.sectionTitleStyle) ??
other.sectionTitleStyle,
separatorDrawer: other.separatorDrawer,
shape: other.shape,
width: other.width,
);
}