Add the type hint for Windows._filter

Helps with type inference of methods like .filter() in Pylance.

Author: Perlence

ahkpy/window.py

@@ -93,7 +93,7 @@ def filter(self, title=UNSET, *, class_name=UNSET, id=UNSET, pid=UNSET, exe=UNSE
         """
         return self._filter(title, class_name, id, pid, exe, text, match)
 
-    def _filter(self, title, class_name, id, pid, exe, text, match):
+    def _filter(self, title, class_name, id, pid, exe, text, match) -> 'Windows':
         if (
             title is UNSET and class_name is UNSET and id is UNSET and pid is UNSET and exe is UNSET and
             text is UNSET and match is None