CI: Add actionlint to check GitHub Action workflow files

[courtneypacheco]

Is your feature request related to a problem? Please describe.
Other repositories within InstructLab utilize actionlint to "lint" (aka validate) GitHub workflow files. I forgot to add actionlint to this repository when creating it. By adding actionlint here, we can not only lint the workfiles within this repository, but we can also lint the in-house action workflow files, too.

Describe the solution you'd like
First, use this actionlint.yml file from the core InstructLab repo, which needs this actionlint.dockerfile and this actionlint.json file to successfully run.

Additional context
N/A