Export ExpectThunk e.g. to Carthage

[DivineDominion]

I noticed that ExpectThunk is only available as a Pod subspec.

Since I don't use CocoaPods, I'm stuck with copying the file. I wonder if it makes sense to add another framework target, e.g. ReSwiftThunkTesting, that exports this type. The RxSwift package is split into RxTesting and all the RxSwift parts as well, and sharing the scheme produces another framework that you can use during tests.

[djsomen]

Bump. I would also like to use ExpectThunk as a Cartharge dependency as we are using Rome caching.

[DivineDominion]

There's a SwiftPM target for this now at least.