merge method
Creates a copy of this heuristics with rules from other appended.
Implementation
ParchmentHeuristics merge(ParchmentHeuristics other) {
return ParchmentHeuristics(
formatRules: formatRules..addAll(other.formatRules),
insertRules: insertRules..addAll(other.insertRules),
deleteRules: deleteRules..addAll(other.deleteRules),
);
}