Searchie API: Add File to include field for Thumbnail URL

Some folks like myself use apps like Placid to auto-generate branded thumbnails for new videos automatically. If Searchie's "Add File" API action had a field for a URL for the thumbnail image, this process could be effortless! At the moment, we need to manually go to each video in Searchie after they've been uploaded and processed, and change each thumbnail one by one. I have 272 to do today!