title: Swift Combine: no `distinct` operator?
body: <p>Seems like Combine (shipped with Xcode 11 beta 7) lacks a <a href="http://reactivex.io/documentation/operators/distinct.html" rel="nofollow noreferrer"><code>distinct</code></a> operator? </p>
  
  <p>Can anyone help me build one? :) </p>