Add missing documentation of wxWindow accessibility functions

Ensure they're present in the interface header as this is also required
for wrapping them in other languages, such as Python.

See #24209.

(cherry picked from commit 81e9373)

interface/wx/window.h

@@ -3438,6 +3438,17 @@ class wxWindow : public wxEvtHandler
     */
     void SetAccessible(wxAccessible* accessible);
 
+    /**
+        Override to create a specific accessible object.
+    */
+    virtual wxAccessible* CreateAccessible();
+
+    /**
+        Returns the accessible object, calling CreateAccessible if necessary.
+        May return NULL, in which case system-provide accessible is used.
+    */
+    wxAccessible* GetOrCreateAccessible();
+
     ///@}