Test in browsers, using eg. GH Actions + Playwright

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See: https://playwright.dev/docs/ci#github-actions

And: https://playwright.dev/docs/test-runners#mocha

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Additional links:

• https://github.com/modernweb-dev/web/blob/HEAD/docs/guides/test-runner/getting-started.md
• https://modern-web.dev/docs/test-runner/test-frameworks/mocha/
• https://modern-web.dev/guides/test-runner/browsers/#testing-in-all-evergreen-browsers
• https://modern-web.dev/docs/test-runner/testing-in-a-ci/
• https://modern-web.dev/docs/test-runner/commands/
• https://github.com/coryrylan/web-test-runner-performance