[doc/ordering] update ordering-family.rst file

Author: bipashabg

doc/ordering/ordering-family.rst

@@ -22,6 +22,7 @@ Ordering - Family of functions
 .. official-start
 
 * :doc:`pgr_cuthillMckeeOrdering` - Return reverse Cuthill-McKee ordering of an undirected graph.
+* :doc:`pgr_sloanOrdering` - Return sloan ordering of an undirected graph.
 * :doc:`pgr_topologicalSort` - Linear ordering of the vertices for directed
   acyclic graph.
 
@@ -31,6 +32,7 @@ Ordering - Family of functions
     :hidden:
 
     pgr_cuthillMckeeOrdering
+    pgr_sloanOrdering
     pgr_topologicalSort
 
 See Also