Add Identifier.AsEntity method

src/gaemstone.ECS/Identifier.cs

@@ -26,6 +26,8 @@ public readonly struct Identifier
 			((relation.Value.Data << 32) & ECS_COMPONENT_MASK) |
 			(   target.Value.Data        & ECS_ENTITY_MASK   )));
 
+	public EntityRef? AsEntity(World world)
+		=> new IdentifierRef(world, this).AsEntity();
 	public (EntityRef Relation, EntityRef Target)? AsPair(World world)
 		=> new IdentifierRef(world, this).AsPair();