Downloads a thumbnail image associated with a document that was previously uploaded to ProjectManager.com.
ProjectManager allows you to store files linked to various elements within your Workspace,
such as Projects, Tasks, or your Home. Files are organized based on their storage location.
When uploading a file, please allow some time for the file to undergo processing and verification.
ProjectManager may reject file uploads containing issues such as malware. Once a file has
completed the upload process, you can retrieve its associated thumbnail using the DownloadThumbnail API.