Rename ListenerCollection::add

[xepozz]

It's better to rename the ListenerCollection::add method to ListenerCollection::withListener because it's not clear that it's immutable

[samdark]

That would be a BC-breaking change.

[xepozz]

Just mark it as deprecated and keep both until the next major version

[Tigrov]

For what purposes is it immutable? If it's a collection, it's nice to be able to just add a listener to it.

[samdark]

To prevent adding listeners via code, not via config.