refactor: moved drawable triangles into systems project for platform agnosticism

Engine.Systems/Graphics/ITriangleBatch.cs

@@ -0,0 +1,10 @@
+using Engine.Core;
+
+namespace Engine.Systems.Graphics;
+
+public interface ITriangleBatch
+{
+    void Begin(Matrix4x4? view = null, Matrix4x4? projection = null);
+    void Draw(Triangle triangle, ColorRGBA colorRGBA);
+    void End();
+}