LWS-159: Run Lighthouse tests on CI

[johanbissemattsson]

Description

Tickets involved

LWS-159

Solves

Runs Lighthouse tests continuously using lighthouse-ci in a GitHub action.

The github action status currently only shows if the tests fails or passes.
We have to self-host a Lighthouse CI server if we want more detailed metrics in the status check.

The Lighthouse CI server can also be used for:

• Store Lighthouse reports for more than a few days
• Keep Lighthouse reports private on your infrastructure
• Generate graphs of improved category scores over time to impress your boss
• Identify regressions in category score or metric performance to specific commits
• View detailed diffs between any two Lighthouse reports to find the root cause of a regression

Summary of changes

• Rename github workflow file
• Format workflow file
• Add lighthouse-ci to github workflow

[johanbissemattsson]

Note to self:
We have to add a LHCI_TOKEN to .github/workflows/lxl-web.yml if we decide to self-host a Lighthouse CI server.

See: https://github.com/GoogleChrome/lighthouse-ci/blob/main/docs/getting-started.md#configuration

[andersju]

Nice! LGTM!