Use Google's Lighthouse via a CI check

Feature request

Google's Lighthouse is a tool used by developers to get a simple measurement on a page's performance, accessibility score, and SEO rating. We should use it via some CI step (CircleCI, GitHub Actions, something else).

Proposed solution

Leverage Lighthouse in this repository's continuous integration against the landing page in a way that lets me confirm that we haven't strayed to far from the scores that https://www.operationcode.org/ is receiving. Also, remember to add the check to the .mergify.yml file so that automated dependency update PRs continue to operate.

Additional context

A quick search yields me many potential tools:

• Lighthouse CI Action
• Lighthouse Check
• Web Performance Audits With Ligthhouse
• Orbs

I think I'd prefer GitHub action so that we're parallelizing CI tasks; however, I'm open to using Orbs or even some other solution. I'll leave the evaluation of the best tool up to you.

Start by reviewing the repository's existing CI configuration and the landing page targeted by the request. Compare Lighthouse CI options, decide how scores should be checked, and update .mergify.yml so dependency update PRs retain the check. Done means CI measures the landing page and flags unacceptable drift from the specified scores.