Fix CI issues

[notlmn]

Take a look at Lighthouse logs for the current build on GitHub Actions and start from there.

Our target scores under each section are:

• Accessibility: 70% (should crank this up to 80%)
• Performance: 85% (should ideally be 90%)
• SEO: 70% (Can crank up to 85%, we are already at 87%)
• Best Practices: 70% (should ideally be 90%, we are already at 93%)

Perform respective changes (image compression and optimization, a11y changes, ...), and increase minimum score targets in test/checklog.js.

Reach out to me (@notlmn) or @r0mflip for any issues or (potentially silly) questions, we won't bite. 😉