Add FAQ and Recipe for Terminal colors (was Demo looks strange)

[Smotrov]

Description

Demo looks strange on MacOS with default font settings in terminal.

To Reproduce

Run following on MacOS cargo run --example=demo2 --features="crossterm widget-calendar"

and you'll see something like on the screenshot.

Expected behavior

Would be good if it will e displayed without glitches.

Screenshots

Environment

MacOS terminal, zsh.

[kdheepak]

Try the demo in iTerm2, Alacritty or Kitty on MacOS. The MacOS default Terminal.app does not support true colors:

https://github.com/ratatui-org/ratatui/blob/935a7187c273e0efc876d094d6247d50e28677a3/src/style/color.rs#L109-L111

duplicate of ratatui/ratatui#475

[joshka]

I'm going to move this over to the website repo and mark it as documentation needed.

• Add a FAQ about RGB color support in terminals
• Add a recipe for detecting support of RGB to avoid this problem