Make possible to define timeouts on smaller parts of Fetch and handle timeouts (or other errors) #429

We can define timeout on entire Fetch after run with cats effect, but I can't find how to define timeout on 'sub' Fetch and handle it with 'default' value. Something like:

(
fetchUser,
fetchPost,
fetchComments.withTimeout(5.secs).handleError(List.empty)
).mapN { (user, post, comments) => 
  EntirePost(user, post, comments)
}

So if fetchComments is too long we can cancel fetching it and return partly constructed structure.