Make the setting of terminal colors optional.

[PhilRunninger]

@Shatur , I love this colorscheme, especially for the fact that it has both dark and light variants. I sometimes try out others, but I always come back to ayu. That being said, I've noticed an area that could be improved. When invoking a :terminal inside of Neovim, ayu sets up some colors that, IMO, don't look so good. The magentas have been lost, and the white isn't bright enough.

This pull request adds an option to disable ayu's setting the g:terminal_color_n values. The new default config is shown here. Setting terminal = false will let the shell use its original colors, while keeping ayu colors in other windows.

local config = {
  defaults = {
    mirage = false,
    terminal = true,
    overrides = {},
  },
}

Before

After

[Shatur]

Thanks!