Add an example of using a custom codeclimate.yml file for a plugin

Problem to solve

The Code Quality docs call out that analysis plugins can be used by code climate but no example is provided showing that the codeclimate.yml file needs to be added nor what can be done so it's hard for users to understand how to extend the default engines.

Further details

I've had several slack pings about how to do this in the last week but a quick read of the page enforces that codeclimate.yml is not mentioned at all.

Proposal

Add a simple example showing the yml that would be added to a codeclimate.yml file to add a plugin and then linking to the codeclimate docs.

Who can address the issue

Anyone!

Other links/references