Added section readme on async

README.md

@@ -89,6 +89,15 @@ iex(11)> ExW3.Contract.call(:SimpleStorage, :get)
 {:ok, 1}
 ```
 
+## Asynchronous
+
+ExW3 now provides async versions of `call` and `send`. They both return a `Task` that can be awaited on.
+
+```elixir
+  t = ExW3.Contract.call_async(:SimpleStorage, :get)
+  {:ok, data} = Task.await(t)
+```
+
 ## Listening for Events
 
 Elixir doesn't have event listeners like say JS. However, we can simulate that behavior with message passing.