Deprecate Window foreign kwarg

Author: ankith26

docs/reST/ref/window.rst

@@ -37,7 +37,6 @@
    :param bool keyboard_grabbed: Create a window with grabbed keyboard input.
    :param bool input_focus: Create a window with input focus.
    :param bool mouse_focus: Create a window with mouse focus.
-   :param bool foreign: Marks a window not created by SDL.
    :param bool allow_high_dpi: Create a window in high-DPI mode if supported.
    :param bool mouse_capture: Create a window that has the mouse captured
                               (unrelated to INPUT_GRABBED).

src_c/window.c

@@ -923,6 +923,12 @@ window_init(pgWindowObject *self, PyObject *args, PyObject *kwargs)
                     }
                 }
                 else if (!strcmp(_key_str, "foreign")) {
+                    if (PyErr_WarnEx(PyExc_DeprecationWarning,
+                                     "The foreign kwarg has been deprecated "
+                                     "and may be removed in a future version",
+                                     1) == -1) {
+                        return -1;
+                    }
                     if (_value_bool) {
                         flags |= SDL_WINDOW_FOREIGN;
                     }