Add EntityBuilder constructor with parent arg

src/gaemstone.ECS/EntityBuilder.cs

@@ -50,6 +50,15 @@ public class EntityBuilder
 	public EntityBuilder(World world, EntityPath? path = null)
 		{ World = world; Path = path; }
 
+	public EntityBuilder(World world, Entity parent, EntityPath? path = null)
+		: this(world, path)
+	{
+		// If given path is absolute, the new entity won't be created as a
+		// child of the specified parent. Alternatively, EntityRef.NewChild
+		// can be used, which will throw when an absolute path is given.
+		if ((path?.IsRelative != false) && parent.IsSome) ChildOf(parent);
+	}
+
 	public override EntityBuilder Add(Id id)
 	{
 		// If adding a ChildOf relation, store the parent separately.

src/gaemstone.ECS/World.cs

@@ -34,18 +34,10 @@ public unsafe partial class World
 
 
 	public EntityBuilder New(EntityPath? path = null)
-		=> new(this, path);
+		=> new(this, default, path);
 
 	public EntityBuilder New(EntityRef? parent, EntityPath? path = null)
-	{
-		var entity = New(path);
-		// If given path is absolute, the new entity won't be created as a
-		// child of the specified parent. Alternatively, EntityRef.NewChild
-		// can be used, which will throw when an absolute path is given.
-		if ((path?.IsRelative != false) && (parent != null))
-			entity.ChildOf(parent);
-		return entity;
-	}
+		=> new(this, parent, path);
 
 
 	public bool Progress(TimeSpan delta)