Local site runner as part of the API

[lanesawyer]

Hi there, I have found this article but not much else on how people are running pa11y in a GitHub Actions-like environment. We're using Node, not Ruby, so that particular article isn't too useful.

It would be super nice if pa11y-ci had a server runner capability, since it's a very common need that would simplify adoption and integration into runners like GitHub Action. Playwright, for example, makes it super easy to test against a local web server.