DOC Add link to plot_swissroll example (scikit-learn#31378)

Author: greygosu

doc/modules/manifold.rst

@@ -115,6 +115,9 @@ from the data itself, without the use of predetermined classifications.
 * See :ref:`sphx_glr_auto_examples_manifold_plot_manifold_sphere.py` for an example of
   manifold learning techniques applied to a spherical data-set.
 
+* See :ref:`sphx_glr_auto_examples_manifold_plot_swissroll.py` for an example of using 
+  manifold learning techniques on a Swiss Roll dataset.
+
 The manifold learning implementations available in scikit-learn are
 summarized below