[2.1] Document immutable event dispatcher

[wouterj]

The ImmutableEventDispatcher cannot be modified. It takes another dispatcher with the listeners and subscribers.

Ideally, it'll be placed in the same document as the Container aware dipatcher.

[xabbuh]

What's the reason to put this into 2.1?

[wouterj]

It's added in 2.1

[xabbuh]

Does this mean we add it also to the 2.1 branch or is this milestone more kind of informal?

[wouterj]

That's something ryan and I cannot agree on with eachother...

Imo, it should be documented in the 2.1 branch.

[weaverryan]

I'm fine with 2.1. Obviously 2.1 is beyond its end of life, but since this is new in 2.1, and since it would represent a new document or at least a new standalone section, the risk to big conflict is low. I think 2.1 should usually be treated as deprecated, but I don't see much harm in bending those rules if we want to push a few things into it. But it should be rare - deprecated branches fall out of sync over time.

Thanks!