ErrorBoundaryFallbackComponent is unnecessary

[blling]

Users will not use the ErrorBoundaryFallbackComponent most of the time, so we can remove it from core lib and put it in a separeted showcase ?

[bvaughn]

That component can be dead-code eliminated from any production app that uses this library without using it, so I don't see the harm in leaving it? It's also tiny. 😄

[bvaughn]

I think I'm going to leave it in for my own convenience (one less project to maintain and sync) and b'c I don't think it's much of a problem, given my previous comment ^

Thanks for raising this issue though!