message: Introduce Util::Sets::contains()
diff: @@ -20,6 +20,15 @@ namespace vcpkg::Util
  }
  }
  + namespace Sets
  + {
  + template<class Container, class T = ElementT<Container>>
  + bool contains(const Container& container, const T& item)
  + {
  + return container.find(item) != container.cend();
  + }
  + }
  +
  template<class Cont, class Func>
  using FmapOut = decltype(std::declval<Func>()(*begin(std::declval<Cont>())));
  