The file widget allows editors to upload a file or select an existing one from the media library. The path to the file will be saved to the field as a string.
-`media_library`: media library settings to apply when a media library is opened by the
current widget
-`allow_multiple`: _(default: `true`)_ when set to `false`, prevents multiple selection for any media library extension, but must be supported by the extension in use
-`config`: a configuration object that will be passed directly to the media library being
used - available options are determined by the library