Fix Style color object for IconStyleOptions. (#87)

- OL js represents RGBA as int array and setting Color breaks JSInterop when string.
- Future extensions could include allowing Color Setting in the SetCustomImageStyle method.
- Setting the style color allows image markers to be tinted.

src/OpenLayers.Blazor/StyleOptions.cs

@@ -172,7 +172,7 @@ public class IconStyleOptions : ImageStyleOptions
         [JsonConverter(typeof(JsonStringEnumKebabLowerConverter))]
         public IconAnchorUnits AnchorYUnits { get; set; }
 
-        public string Color { get; set; }
+        public int[] Color { get; set; }
 
         public string CrossOrigin { get; set; }
         public double? Width { get; set; }