Add an example in the wiki to demonstrate how to run on an array of paths

[louim]

Hey!
I think it would be helpful to add an example like this in the CLI page. I was looking in how to add the Gemfile to the parsed paths.

ENABLE_SMART_TODO=1 bundle exec smart_todo Gemfile . --fallback_channel '#general' --slack_token 'abc'

[Edouard-chin]

Done, thanks 🙇