Draws a line in the world. Only use for debugging purposes!
If the duration isn't set to 0, this function will return nil and the line will be removed after the duration has passed.
Otherwise the line will automatically removed when all references to it are destroyed, or DebugRendererObject:Remove is called.
If this function is run serverside, it will always return nil. (Using a duration of 0 will be pointless in this case.)