message: doc(UMDExample): Add polyData support
diff: function processFile(event) {
  - var outputTextArea = document.querySelector("textarea");
  + const outputTextArea = document.querySelector("textarea");
  outputTextArea.textContent = "Loading...";
  - var dataTransfer = event.dataTransfer;
  - var files = event.target.files || dataTransfer.files;
  + const dataTransfer = event.dataTransfer;
  + const files = event.target.files || dataTransfer.files;
  - return itk.readFile(null, files[0]).then(function({ image, mesh, webWorker }) {
  + return itk.readFile(null, files[0]).then(function({ image, mesh, polyData, webWorker }) {
  webWorker.terminate();
  - var imageOrMesh = image || mesh;
  + var imageOrMeshOrPolyData = image || mesh || polyData;
  function replacer(key, value) {
  if (!!value && value.byteLength !== undefined) {
  @@ -15,6 +15,6 @@ function processFile(event) {
  }
  return value;
  }
  - outputTextArea.textContent = JSON.stringify(imageOrMesh, replacer, 4);
  + outputTextArea.textContent = JSON.stringify(imageOrMeshOrPolyData, replacer, 4);
  });
  }
  