COMPMID-1750: Add PriorBox operator to graph API.

Change-Id: I5d2ed5dcc342abff8124762f7bdee587cdf20032
diff --git a/arm_compute/graph/nodes/Nodes.h b/arm_compute/graph/nodes/Nodes.h
index 342ecbf..5c7599f 100644
--- a/arm_compute/graph/nodes/Nodes.h
+++ b/arm_compute/graph/nodes/Nodes.h
@@ -45,6 +45,7 @@
 #include "arm_compute/graph/nodes/PadLayerNode.h"
 #include "arm_compute/graph/nodes/PermuteLayerNode.h"
 #include "arm_compute/graph/nodes/PoolingLayerNode.h"
+#include "arm_compute/graph/nodes/PriorBoxLayerNode.h"
 #include "arm_compute/graph/nodes/ROIAlignLayerNode.h"
 #include "arm_compute/graph/nodes/ReorgLayerNode.h"
 #include "arm_compute/graph/nodes/ReshapeLayerNode.h"