mergeList method
Merges this list with other. If unique is true, duplicates are
excluded.
Implementation
List<T> mergeList(List<T> other, {bool unique = false}) {
if (!unique) return [...this, ...other];
final result = [...this];
for (final e in other) {
if (!result.contains(e)) result.add(e);
}
return result;
}