Add Dictionary.merge()

core/variant/dictionary.cpp

@@ -269,6 +269,14 @@ void Dictionary::clear() {
 	_p->variant_map.clear();
 }
 
+void Dictionary::merge(const Dictionary &p_dictionary, bool p_overwrite) {
+	for (const KeyValue<Variant, Variant> &E : p_dictionary._p->variant_map) {
+		if (p_overwrite || !has(E.key)) {
+			this->operator[](E.key) = E.value;
+		}
+	}
+}
+
 void Dictionary::_unref() const {
 	ERR_FAIL_COND(!_p);
 	if (_p->refcount.unref()) {