Support random color scheme, pseudocode [ scheme = rand(settings.schemes) ]

# Description of the new feature/enhancement

There is a site [https://windowsterminalthemes.dev/](https://windowsterminalthemes.dev/), it shares many awesome color themes. I choose some of them, pasted in settings.schemes, then I may change the colorScheme daily depends on my feeling.

The `Oh-My-Zsh` has a similar feature, the random theme, a theme will be chosen randomly every time a new shell is opened.

Wish Windows Terminal could have something like that.

# Proposed technical implementation details (optional)

Introduce a keyword like `random`, if the colorScheme field is set to random, then every time a new tag or window is opened, randomly choose a color schema from settings.schemes .

Start by reviewing how the colorScheme setting and settings.schemes are handled when a new tab or window opens. Confirm the expected behavior for a random selection, including whether selection occurs per new tab or window, and verify that choosing random produces a scheme from settings.schemes.

Written by the indexing model from the issue text.