Output hex color value for transparent values if `UseHex` is true

[mganss]

Currently, when UseHex is true, color values are output as hex only if alpha is 1.0.

AngleSharp.Css/src/AngleSharp.Css/Values/Primitives/Color.cs

Lines 376 to 381 in 15deaee

	/// <summary>
	/// Gets or sets if hex codes should be used for serialization.
	/// This will not be applied in case of transparent colors, i.e.,
	/// when alpha is not 1.
	/// </summary>
	public static Boolean UseHex { get; set; }

AngleSharp.Css/src/AngleSharp.Css/Values/Primitives/Color.cs

Lines 398 to 401 in 15deaee

	else if (_alpha == 255 && UseHex)
	{
	return $"#{_red.ToString("X2", CultureInfo.InvariantCulture)}{_green.ToString("X2", CultureInfo.InvariantCulture)}{_blue.ToString("X2", CultureInfo.InvariantCulture)}";
	}

Perhaps this could be changed to include colors with alpha < 1.0, too.

[FlorianRappl]

Implemented and available in next preview / 1.0.0.