add configparser.RawConfigParser.converters (#13146)

stdlib/configparser.pyi

@@ -277,6 +277,8 @@ class RawConfigParser(_Parser):
     def remove_option(self, section: str, option: str) -> bool: ...
     def remove_section(self, section: str) -> bool: ...
     def optionxform(self, optionstr: str) -> str: ...
+    @property
+    def converters(self) -> ConverterMapping: ...
 
 class ConfigParser(RawConfigParser):
     # This is incompatible with MutableMapping so we ignore the type