Add HTTPX (#6)

README.md

@@ -46,6 +46,7 @@ _Libraries for use in ASGI apps._
 - [Ariadne](https://github.com/mirumee/ariadne) - A Python library for implementing GraphQL servers.
 - [asgiref](https://github.com/django/asgiref) - ASGI reference implementation, including function wrappers, server base classes and a WSGI-to-ASGI adapter.
 - [Bonnette](https://github.com/erm/bonnette) - ASGI adapter for Azure Functions.
+- [HTTPX](https://www.encode.io/httpx) - Next generation HTTP client, including async support and ability to call ASGI apps directly.
 - [Mangum](https://github.com/erm/mangum) - AWS Lambda & API Gateway support for ASGI.
 - [tartiflette-starlette](https://github.com/tartiflette/tartiflette-starlette) - ASGI support for the Tartiflette GraphQL engine.