Imports typing during conversion of struct code to Dict

Author: mxthxngx

protobuf_to_pydantic/plugin/field_desc_proto_to_code.py

@@ -623,6 +623,7 @@ def _get_type_factory(module_name: str, message_name: str) -> Any:
                 py_type_str = "typing.Dict"
                 rule_type_str = "struct"
                 type_factory = dict
+                self._add_import_code("typing")
             elif field.type_name.startswith(".google.protobuf"):
                 py_type_str = _type_str
                 rule_type_str = "any"