added onRender as a drawPoints property and as a function on the object itself

lib/timeline/optionsGraph2d.js

@@ -51,9 +51,10 @@ let allOptions = {
   },
   drawPoints: {
     enabled: {boolean},
+    onRender: { 'function': 'function' },
     size: {number},
     style: {string:['square','circle']}, // square, circle
-    __type__: {object,boolean}
+    __type__: {object,boolean,'function': 'function'}
   },
   dataAxis: {
     showMinorLabels: {boolean},