Request: color scheme browser

[mikemaccana]

Discussed a little bit in other threads, but I thought I'd add an issue as all iTerm2 color schemes have been ported to Windows Terminal.

Summary of the new feature/enhancement

Add a color scheme browser.

• User hits Settings - Themes, and types 'Monokai Soda'
• User sees a preview on the color scheme (dynamically fetched from an online source)
• They click apply,

Benefits

This means:

• Windows Terminal isn't limited to a small amount of inbuilt color scheme
• Users don't have to use or know about colortool
• Users who want to use a well known theme can just type the color scheme's name and use the colopr scheme

[DHowett-MSFT]

Probably in the future, but we should just talk about it as part of #1564 and #555 (plugin market, etc.)

[mikemaccana]

Sure will move there 👍