Extend namespace package support to tcod.sdl

In case any SDL tools such as audio mixing are put in another package.

Fix typo.

Author: HexDecimal

CHANGELOG.md

@@ -4,6 +4,8 @@ Changes relevant to the users of python-tcod are documented here.
 This project adheres to [Semantic Versioning](https://semver.org/) since version `2.0.0`.
 
 ## [Unreleased]
+### Added
+- Added support for `tcod.sdl` namespace packages.
 
 ## [15.0.0] - 2023-01-04
 ### Changed

tcod/sdl/__init__.py

@@ -1,10 +1,13 @@
 from __future__ import annotations
 
 import logging
+from pkgutil import extend_path
 from typing import Any, Callable, Tuple, TypeVar
 
 from tcod.loader import ffi, lib
 
+__path__ = extend_path(__path__, __name__)
+
 T = TypeVar("T")
 
 logger = logging.getLogger(__name__)
@@ -59,7 +62,7 @@ def _linked_version() -> Tuple[int, int, int]:
 
 
 def _version_at_least(required: Tuple[int, int, int]) -> None:
-    """Raise an error if the compiled version is less than required.  Used to guard recentally defined SDL functions."""
+    """Raise an error if the compiled version is less than required.  Used to guard recently defined SDL functions."""
     if required <= _compiled_version():
         return
     raise RuntimeError(