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

[Michael Ganss]

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.