Accept type like: ``` accept = '.json' ``` in https://github.com/rdmorganiser/rdmo-plugins/blob/1a99b6f26cd87dbda9ed5c4c1ba02fdc775c05f2/rdmo_plugins/imports/madmp.py#L10 similar to https://github.com/rdmorganiser/rdmo/blob/c945d7d9ef5efdccb2d7b41b914ff50ea6f7b49c/rdmo/projects/imports.py#L90
