Add _add_alias_ for name aliases.

Author: tjdcs

stdlib/enum.pyi

@@ -220,7 +220,10 @@ class Enum(metaclass=EnumMeta):
         @classmethod
         def __signature__(cls) -> str: ...
     if sys.version_info >= (3, 13):
+        # Value may be any type, even in special enums. Enabling Enum parsing from
+        # multiple value types
         def _add_value_alias_(self, value: Any) -> None: ...
+        def _add_alias_(self, name: str) -> None: ...
 
 if sys.version_info >= (3, 11):
     class ReprEnum(Enum): ...