Add custom ansi colors and CSS variables for them

[silverwind]

Use our existing color palette to map to the 16 basic ansi colors. This is backwards-compatible because it aliases the existing color names.

Side note: I think the colors in console.css for console file rendering are incomplete, but fixing those is out of scope here imo.

Before and after:

[wxiaoguang]

Does it affect 256 and other colors?

[silverwind]

No, only 16 colors. 256 colors and above still use inline style and I don't think ansi_up supports classes for those either. It's validated in this existing test:

  expect(renderAnsi('\x1b[48;5;88ma\x1b[38;208;48;5;159mb\x1b[m')).toEqual(`<span style="background-color:rgb(135,0,0)">a</span><span style="background-color:rgb(175,255,255)">b</span>`);