Feedback EntityCommandBuffer.AddDynamicComponent

I'm writing some generic systems and there are few issues I've encountered.

I cannot create generic job, without knowing up-front all concrete instantiations (fair point)/
So I tried using `DynamicComponentTypeHandle` to do some work on generic components.

I can write component data easily (e.g. by passing NativeArray<byte> into job and copying bytes).
But I cannot add component with data, because no overload of EntityCommandBuffer supports that.

Can you please add something like:
`EntityCommandBuffer.AddComponent(Entity e, ComponentType type, NativeArray<byte> data)`

And similar overload for ECB.ParallerWriter

This would help a lot!

It should be easily doable, because ECB just copies component data into stream anyway, instead of copying from `T` it would copy from `NativeArray<byte>`

Thanks!