feat(XamlX): Trim text before invoke Color.Parse (#16649)

* test: Add falling test case

* feat(XamlX): trim text before invoke Color.Parse

src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/AvaloniaXamlIlLanguageParseIntrinsics.cs

@@ -172,6 +172,7 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions
 
             if (type.Equals(types.Color))
             {
+                text = text.Trim();
                 if (!Color.TryParse(text, out Color color))
                 {
                     return ReturnOnParseError($"Unable to parse \"{text}\" as a color", out result);

tests/Avalonia.Markup.Xaml.UnitTests/Xaml/AvaloniaIntrinsicsTests.cs

@@ -108,6 +108,24 @@ public class AvaloniaIntrinsicsTests : XamlTestBase
             Assert.Contains(contains, runtimeXamlDiagnostic.Title, StringComparison.OrdinalIgnoreCase);
         }
     }
+
+    /// <summary>
+    /// GitHub Issue <see href="https://github.com/AvaloniaUI/Avalonia/issues/15320">#15320</see>
+    /// </summary>
+    [Fact]
+    public void Should_Parse_Formatted_Color_Tag()
+    {
+        var target = AvaloniaRuntimeXamlLoader
+                .Parse<ResourceDictionary>($"""
+                                            <ResourceDictionary xmlns="https://github.com/avaloniaui"
+                                                                xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
+                                                <Color x:Key="ColorKey">
+                                                    White
+                                                </Color>
+                                            </ResourceDictionary>
+                                            """);
+        Assert.NotNull(target);
+    }
 }
 
 public class TestIntrinsicsControl : Control