Add macros to thread using promises

[wilkerlucio]

Hello, first thanks a lot for this project, it makes my like with async so nice :)

There are these 2 macros that I made to help do thread on async operations, they are very helpful to me and I think they could be in the Promesa itself, here they go:

(defmacro p-> [x & forms]
  (let [fns (mapv (fn [arg]
                    (let [[f & args] (if (sequential? arg)
                                       arg
                                       (list arg))]
                      `(fn [p#] (~f p# ~@args)))) forms)]
    `(p/chain (p/promise ~x) ~@fns)))

(defmacro p->> [x & forms]
  (let [fns (mapv (fn [arg]
                    (let [[f & args] (if (sequential? arg)
                                       arg
                                       (list arg))]
                      `(fn [p#] (~f ~@args p#)))) forms)]
    `(p/chain (p/promise ~x) ~@fns)))

With these macros we can thread as if it was sync, but using promises, like:

(p-> (js/fetch "...")
     (gobj/get "body"))

If you think this is an interesting addition I can send a PR including tests.

Cheers.

[niwinz]

Interesting, sorry for late response, i was busy and only looked for critical bugs.

They are pretty interesting macros, if you still interested in make a PR, it will be very welcome.