message: doc(UMDExample): Bump to 1.0.0-b.6
diff: <title>itk-wasm UMD Example</title>
  <meta charset="UTF-8" />
  <link rel="stylesheet" href="styles.css">
  - <script src="https://cdn.jsdelivr.net/npm/itk-wasm@1.0.0-b.3/dist/umd/itk-wasm.min.js"></script>
  + <script src="https://cdn.jsdelivr.net/npm/itk-wasm@1.0.0-b.6/dist/umd/itk-wasm.min.js"></script>
  <script src="https://unpkg.com/itk-vtk-viewer@9.23.2/dist/itkVtkViewerCDN.js"></script>
  </head>
  