[Common Lisp] Add CI for validating the track

[verdammelt]

Getting started

Please please please read the docs before starting. Posting PRs without reading these docs will be a lot more frustrating for you during the review cycle, and exhaust Exercism's maintainers' time. So, before creating the issue, please read up on the following documents:

• The features of v3.
• Rationale for v3.
• What are concept exercise and how they are structured?

Please also watch the following video:

• The Anatomy of a Concept Exercise.

Goal

The Common Lisp track needs CI action(s) to validate the track:

• [ ] run configlet linting
• [ ] ensure all example files pass their tests

[verdammelt]

The CI could do more things, we can discuss here before creating solutions. I feel that checking examples pass the solution is the least it should do (this was already a problem).

[verdammelt]

I am going to close this issue since in a few weeks' time the common lisp track of the v3 repo will be ripped out and PR'd on top of the v2 track... which has this sort of CI system already.