Colorizer like plugin as a built-in

[txtyash]

There's a plugin https://github.com/norcalli/nvim-colorizer.lua for neovim that previews the colors.

This is quite useful in CSS files as well as TOML files for Helix's themes.

This way users can easily create and edit themes in helix itself.

It can be restricted to certain files or toggled with a command.

[the-mikedavis]

Duplicate of #1115

Also, #2823