added httpx to the list of adapters (#3)

It has been listed for a while in faraday website, but no mention here. This PR changes that.

README.md

@@ -20,6 +20,8 @@ The following table show the available adapters and which features they support.
 | [Patron] | v1 only | ✔️ | ✖️ | ✖️ | ✖️ | ✖️ | ✔️ | ✖️ | ✖️ |
 | [Typhoeus] | v1 only | ✖️ | ✖️ | ✖️ | ✔️ | ✔️ | ✔️ | ✔️ | ✖️ |
 | [HTTP.rb] | ✖️ | ✔️ | ✖️ | ✖️ | ✖️ | ✔️ | ✖️ | ✔️ | ✔️ |
+| [httpx] | ✖️ | ✔️ | ✔️ | ✔️ | ✔️ | ✔️ | ✔️ | ✔️ | ✔️ |
+
 
 ## Middleware
 
@@ -84,3 +86,4 @@ TBC
 [Patron]: https://github.com/lostisland/faraday-patron
 [Typhoeus]: https://github.com/typhoeus/typhoeus/blob/master/lib/typhoeus/adapters/faraday.rb
 [HTTP.rb]: https://github.com/lostisland/faraday-http
+[httpx]: https://honeyryderchuck.gitlab.io/httpx/wiki/Faraday-Adapter