code: function lightenColor(col, amount) {
    let colRgba = parseColor(col);
    let colHsla = rgbaToHsla(colRgba.r, colRgba.g, colRgba.b, colRgba.a);
    colRgba = hslaToRgba(colHsla[0],colHsla[1],Math.min(Math.max(colHsla[2]+amount, 0), 1),colHsla[3]);
    return RGBobj2string({
      r: colRgba[0],
      g: colRgba[1],
      b: colRgba[2],
      a: colRgba[3]
    });
  }
docs: Increase colour lightness by the given amount.