Add Enterprise

[marcinzh]

1. Add Enterprise
2. Fix formatting of my last submission: Turbolift (missing 2 spaces)

[yallop]

I think Enterprise doesn't quite fit here. Libraries that implement effects and handlers (particularly if use notable implementation techniques, and particularly if they're used by others) are in scope, but libraries that simply use algebraic effects and handlers aren't.

[marcinzh]

Well, I suppose I took "theory and practice" part of the decription too literally.

[yallop]

Not too literally, exactly, just more broadly than we intended. Thank you for the PR; I've pulled out the formatting change into #177 to merge separately.