[Site] dark/light Theme for https://platform.uno

[workgroupengineering]

What would you like to be added:

Implementation of the dark theme for the site and automatic identification based on the OS / Browser settings

Why is this needed:

improve the readability of the site

For which Platform:

• [ ] iOS
• [ ] Android
• [ ] WebAssembly
• [ ] WebAssembly renderers for Xamarin.Forms
• [ ] macOS
• [ ] Skia
  • [ ] WPF
  • [ ] GTK (Linux)
  • [ ] Tizen
• [ ] Windows
• [ ] Build tasks
• [ ] Solution Templates

Anything else we need to know?

Some references:

• https://www.hanselman.com/blog/how-to-detect-if-the-users-os-prefers-dark-mode-and-change-your-site-with-css-and-js
• https://stackoverflow.com/questions/50840168/how-to-detect-if-the-os-is-in-dark-mode-in-browsers
• https://flaviocopes.com/javascript-detect-dark-mode/

[elibroftw]

This may be helpful https://github.com/perlun/darkerfx

GitHub

GitHub - perlun/darkerfx: A dark theme for documentation generated with DocFX, similar to darkfx

A dark theme for documentation generated with DocFX, similar to darkfx - GitHub - perlun/darkerfx: A dark theme for documentation generated with DocFX, similar to darkfx

[MartinZikmund]

CC @mtmattei