Convert nice html color codes into terminal colors
e.g. to make ruco colorful 😀

    COLOR_SOURCE_VALUES = 256
    COLOR_TARGET_VALUES = 5
    COLOR_DIVIDE = COLOR_SOURCE_VALUES / COLOR_TARGET_VALUES
    TERM_COLOR_BASE = 16

    # '#ff0000' => 196
    def self.html_to_terminal_color(html_color)
      return unless html_color
      r = (html_color[1..2].to_i(16) / COLOR_DIVIDE) * 36
      g = (html_color[3..4].to_i(16) / COLOR_DIVIDE) * 6
      b = (html_color[5..6].to_i(16) / COLOR_DIVIDE) * 1
      TERM_COLOR_BASE + r + g + b
    end