Add fullscreen property to Renderer. Still needs to be properly implemented for RaylibRenderer.

DaggerFramework/Source/Rendering/StandardRenderer.cs

@@ -12,7 +12,7 @@ namespace DaggerFramework.Rendering
     public class StandardRenderer : Renderer
     {
         /// <inheritdoc />
-        public override Vector2 WindowSize => throw new NotImplementedException();
+        public override Vector2 WindowSize { get; set; }
         /// <inheritdoc />
         public override bool ShouldRun => throw new NotImplementedException();
 
@@ -21,6 +21,8 @@ namespace DaggerFramework.Rendering
         public override int TargetFps { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
         public override bool VSync { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
         public override string WindowTitle { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
+        public override bool Fullscreen { get => throw new NotImplementedException(); set => throw new NotImplementedException(); }
+