merge method
Returns a new ThemeConfig that is
a combination of this object and the given other
style.
Implementation
ThemeConfig merge(ThemeConfig? other) {
// if null return current object
if (other == null) return this;
return copyWith(
light: other.lightData,
dark: other.darkData,
extensionBuilder: other.extensionBuilder,
description: other.description,
);
}