Review dark mode colors

[countableSet]

I'm still not totally happy with it. I wonder if there's some tweaks we can do to it.

The contrast between the background, sidebar, header, and text color still 'feel' off.

[countableSet]

samples

• https://docs.spring.io/spring-boot/docs/current/reference/html/getting-started.html#getting-started
• https://mui.com/material-ui/getting-started/overview/
• https://developers.cloudflare.com/registrar/why-choose-cloudflare/custom-domain-protection/
• https://docs.microsoft.com/en-us/sharepoint/corporate-communications-overview
• https://docs.github.com/en/actions/examples/using-scripts-to-test-your-code-on-a-runner
• https://pkg.go.dev/crypto/tls