getBlob()

This method is useful for sending a SoundFile to a server. It returns the .wav-encoded audio data as a "Blob". A Blob is a file-like data object that can be uploaded to a server with an http request. We'll use the httpDo options object to send a POST request with some specific options: we encode the request as multipart/form-data, and attach the blob as one of the form values using FormData.