Add example with non-standard formatters

README.md

@@ -55,3 +55,13 @@ Defines custom parameter types.
 ### reuse
 
 Suggests a way to reuse step definitions.
+
+### formatter
+
+Uses non-default output formatter. See
+[package.json](https://github.com/caraus-ecms/cucumber-js-demo/blob/master/formatter/package.json).
+
+See also:
+
+- Custom formatters: https://github.com/cucumber/cucumber-js/blob/master/docs/custom_formatters.md
+- Built-in formatters: https://github.com/cucumber/cucumber-js/tree/master/src/formatter.