add nbgallery in point_25d example section

Author: fs446

sfs/fd/wfs.py

@@ -217,6 +217,12 @@ def point_25d(omega, x0, n0, xs, xref=[0, 0, 0], c=None, omalias=None):
         normalize_gain = 4 * np.pi * np.linalg.norm(xs)
         plot(normalize_gain * d, selection, secondary_source)
 
+    .. nblinkgallery::
+        :caption: Further Example
+        :name: wfs-referencing-link-gallery
+
+        examples/wfs-referencing
+
     """
     x0 = _util.asarray_of_rows(x0)
     n0 = _util.asarray_of_rows(n0)