avalonia: Added DateTimeToBooleanConverter

InABox.Avalonia/Converters/DateTimeToBooleanConverter.cs

@@ -0,0 +1,14 @@
+using System;
+using InABox.Core;
+
+namespace InABox.Avalonia.Converters;
+
+public class DateTimeToBooleanConverter : AbstractConverter<DateTime, bool>
+{
+    public static readonly DateTimeToBooleanConverter Instance = new DateTimeToBooleanConverter();
+
+    protected override bool Convert(DateTime value, object? parameter = null)
+    {
+        return !value.IsEmpty();
+    }
+}