Add serializer for RectangleF

src/cs/MonoGame.Extended/Serialization/RectangleFJsonConverter.cs

@@ -0,0 +1,24 @@
+using System;
+using Newtonsoft.Json;
+
+namespace MonoGame.Extended.Serialization;
+
+public class RectangleFJsonConverter: JsonConverter
+{
+    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
+    {
+        var rect = (RectangleF)value;
+        writer.WriteValue($"{rect.Left} {rect.Top} {rect.Width} {rect.Height}");
+    }
+
+    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
+    {
+        var values = reader.ReadAsMultiDimensional<float>();
+        return new RectangleF(values[0], values[1], values[2], values[3]);
+    }
+
+    public override bool CanConvert(Type objectType)
+    {
+        return objectType == typeof(RectangleF);
+    }
+}