doc: add compatibility anchor for ImageSlide section

bgilbert · bgilbert · commit c0315a5173d9 · 2023-07-22T01:28:29.000-04:00
Support old links from before 1f58432 changed the section title. Signed-off-by: Benjamin Gilbert <bgilbert@cs.cmu.edu>
diff --git a/doc/index.rst b/doc/index.rst
@@ -346,6 +346,8 @@ Exceptions
    Subclass of :exc:`OpenSlideError`.
 
 
+.. _wrapping-a-pil-image:
+
 Wrapping a Pillow Image
 =======================
 
