use antialias setting in static gl2d contexts

Author: etpinard

shelly/plotlyjs/static/plotlyjs/src/gl2d/scene2d.js

@@ -75,7 +75,8 @@ proto.makeFramework = function() {
             try {
                 STATIC_CONTEXT = STATIC_CANVAS.getContext('webgl', {
                     preserveDrawingBuffer: true,
-                    premultipliedAlpha: true
+                    premultipliedAlpha: true,
+                    antialias: true
                 });
             } catch(e) {
               throw new Error([