📝 describe how to list CLI products (#149)

Author: ianardee

README.md

@@ -208,15 +208,17 @@ puts result.document
 A command-line interface tool is available to quickly test documents:
 
 ```sh
-ruby ./bin/mindee.rb invoice path/to/your/file.ext
+ruby ./bin/mindee.rb <product_name> path/to/your/file.ext
 ```
 
 Using the ruby bundler:
 
 ```sh
-bundle exec ruby ./bin/mindee.rb invoice path/to/your/file.ext
+bundle exec ruby ./bin/mindee.rb <product_name> path/to/your/file.ext
 ```
 
+Where possible values for `<product_name>` can be displayed by running the command with no arguments.
+
 ## Further Reading
 
 There's more to it than that for those that need more features, or want to