fix(rect): Allow the usage of spaces for components of a Rect (used in a <RectangleGeometry>)

Author: carldebilly

src/Uno.Foundation/Rect.cs

@@ -107,9 +107,15 @@ public static implicit operator Rect(string text)
 			}
 
 			var parts = text
-				.Split(new[] { ',' })
+				.Split(new[] { ',', ' ' })
 				.SelectToArray(s => double.Parse(s, NumberFormatInfo.InvariantInfo));
 
+			if(parts.Length != 4)
+			{
+				throw new ArgumentException(
+					"Cannot create a Rect from " + text + ": needs 4 parts separated by a comma or a space.");
+			}
+
 			return new Rect
 			(
 				parts[0],