Post-upgrade improvements

[cristinecula]

I still think you should drop the unsubscribeFromEvents call from the source effect destructor
if a source is closed, it won't trigger events anyway
you might as well unsubscribe after closing, it won't matter
this would separate and contain the implementation of the two effects, leading to easier maintenance
I would even wrap the two effects in two useHook-style functions and export those too, along with the component
if someone wants the logic without the component, they are free to use it

Re https://neovici.slack.com/archives/DGX65MV34/p1586154405055700 (private)
Re #33