message: add attachmentLayout
diff: @@ -46,6 +46,7 @@ interface BotkitMessageTemplate {
  attachments?: ((template: any, vars: any) => any[]) | any[];
  blocks?: ((template: any, vars: any) => any[]) | any[];
  attachment?: ((template: any, vars: any) => any) | any;
  + attachmentLayout?: string;
  channelData?: any;
  collect: {
  key?: string;
  