message: Update js_usage.markdown to use onRuntimeInitialized
  The Emscripten library is not guaranteed to be fully loaded during the
  script element's onload event. Module.onRuntimeInitialized seems to be
  more reliable.
diff: @@ -122,11 +122,14 @@ imgElement.onload = function() {
  mat.delete();
  };
  -function onOpenCvReady() {
  +var Module = {
  + // https://emscripten.org/docs/api_reference/module.html#Module.onRuntimeInitialized
  + onRuntimeInitialized() {
  document.getElementById('status').innerHTML = 'OpenCV.js is ready.';
  }
  +};
  </script>
  -<script async src="opencv.js" onload="onOpenCvReady();" type="text/javascript"></script>
  +<script async src="opencv.js" type="text/javascript"></script>
  </body>
  </html>
  @endcode
  