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.
* **Name:** `file`
* **UI:** file picker button opens media gallery
* **Data type:** file path string
* **Options:**
* `default`: accepts a file path string; defaults to null
* `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
* `media_folder`(Beta): file path where uploaded files will be saved specific to this control. Paths can be relative to a collection folder (e.g.`files`will add the file to a sub-folder in the collection folder) or absolute with reference to the base of the repo which needs to begin with`/`(e.g`/static/files`will save uploaded files to the`static`folder in a sub folder named`files`)
* `choose_url`: *(default: `true`)* when set to `false`, the "Insert from URL" button will be hidden
