Generic sitemap (#1198)

* Add test for both issue cases

* Use generic type and add new django 4.1 `get_latest_lastmod` method

* Add Sitemap to monkeypatch

* Update test case to use generic + add failing case

* Test GenericSitemap too

django_stubs_ext/django_stubs_ext/patch.py

@@ -4,6 +4,7 @@ from typing import Any, Generic, Iterable, List, Optional, Tuple, Type, TypeVar
 from django import VERSION as VERSION
 from django.contrib.admin import ModelAdmin
 from django.contrib.admin.options import BaseModelAdmin
+from django.contrib.sitemaps import Sitemap
 from django.contrib.syndication.views import Feed
 from django.core.files.utils import FileProxyMixin
 from django.core.paginator import Paginator
@@ -60,6 +61,7 @@ _need_generic: List[MPGeneric[Any]] = [
     MPGeneric(BaseModelForm),
     MPGeneric(BaseModelFormSet),
     MPGeneric(Feed),
+    MPGeneric(Sitemap),
     MPGeneric(FileProxyMixin),
     MPGeneric(Lookup),
     # These types do have native `__class_getitem__` method since django 3.1: