code: public ResponseBuilder addDirective(Directive directive) {
          if (directiveList == null) {
              directiveList = new ArrayList<>();
          }
          directiveList.add(directive);
  
          return this;
      }
docs: Adds a given {@link Directive} to the response.
  
  @param directive directive to send with the response back to the Alexa device
  @return response builder