Add browser-side performance and UI testing

[aensley]

Types of tests:

• Load time
• Performance
• Functionality/errors
• SEO

Links:

• https://testingbot.com/open-source
• https://pagespeed.web.dev/
• https://developers.google.com/web/tools/lighthouse/
• https://github.com/GoogleChrome/lighthouse-ci/blob/main/docs/getting-started.md
• https://web.dev/fast/
• https://gtmetrix.com/
• https://www.webpagetest.org/
• https://tools.pingdom.com/
• https://sitechecker.pro/speed-test/
• https://sitechecker.pro/website-crawler/
• https://sitechecker.pro/website-monitoring/
• https://sematext.com/blog/website-performance-speed-test-tools/