some new files

test/worker.js

@@ -0,0 +1,33 @@
+// Can we start Konva inside worker?
+
+importScripts('../../konva.js');
+console.log(Konva);
+
+Konva.Util.createCanvasElement = () => {
+  const canvas = new OffscreenCanvas(100, 100);
+  canvas.style = {};
+  return canvas;
+};
+
+Konva.Canvas.prototype.setSize = function(width, height) {
+  this.setWidth(width || 1);
+  this.setHeight(height || 1);
+};
+
+Konva.Stage.prototype._checkVisibility = function() {};
+
+var stage = new Konva.Stage({
+  width: 100,
+  height: 100
+});
+
+var layer = new Konva.Layer();
+stage.add(layer);
+
+var shape = new Konva.Circle({
+  x: stage.width() / 2,
+  y: stage.height() / 2,
+  radius: 50,
+  fill: 'red'
+});
+layer.add(shape);