Set background color using 24bit rgb. color can be a number in range 0x000000 to 0xffffff or an Rgb.

To produce the color magenta:

     import { bgRgb24 } from "https://deno.land/std@0.224.0/fmt/colors.ts";
     bgRgb24("foo", 0xff00ff);
     bgRgb24("foo", {r: 255, g: 0, b: 255});