feat: add loading.

src/Ursa/Controls/Loading/Loading.cs

@@ -0,0 +1,26 @@
+using Avalonia;
+using Avalonia.Controls;
+
+namespace Ursa.Controls;
+
+public class Loading: ContentControl
+{
+    public static readonly StyledProperty<object?> IndicatorProperty = AvaloniaProperty.Register<Loading, object?>(
+        nameof(Indicator));
+
+    public object? Indicator
+    {
+        get => GetValue(IndicatorProperty);
+        set => SetValue(IndicatorProperty, value);
+    }
+
+    public static readonly StyledProperty<object?> IsLoadingProperty = AvaloniaProperty.Register<Loading, object?>(
+        nameof(IsLoading));
+
+    public object? IsLoading
+    {
+        get => GetValue(IsLoadingProperty);
+        set => SetValue(IsLoadingProperty, value);
+    }
+    
+}