STYLE: add geometric constraint to decomposeParDict example (issue #921)

applications/utilities/parallelProcessing/decomposePar/decomposeParDict

@@ -231,6 +231,34 @@ constraints
         type    refinementHistory;
         enabled false;
     }
+    geometric
+    {
+        type    geometric;
+
+        grow    false;
+
+        selection
+        {
+            box1
+            {
+                source  box;
+                min     (-0.1 -0.01 -0.1);
+                max     (0.1 0.30 0.1);
+            }
+            ball
+            {
+                source  sphere;
+                origin  (-0.1 -0.01 -0.1);
+                radius  0.25;
+            }
+            blob
+            {
+                source      surface;
+                surfaceType triSurfaceMesh;
+                surfaceName blob.obj;
+            }
+        }
+    }
 }
 */