Add asgiproxy to Proxies (#73)

Co-authored-by: Florimond Manca <florimond.manca@protonmail.com>

README.md

@@ -94,10 +94,11 @@ _Packages for monitoring ASGI web applications._
 
 ## Proxies
 
-_Packages for use when running ASGI web applications behind proxies._
+_Packages for use when running ASGI web applications behind proxies, or proxying other servers via ASGI applications._
 
 <!-- sort_by:name -->
 
+- [asgiproxy](https://github.com/valohai/asgiproxy) – Tools for building HTTP and Websocket proxies for ASGI.
 - [ProxyHeadersMiddleware](https://github.com/encode/uvicorn/blob/master/uvicorn/middleware/proxy_headers.py) - Use `X-Forwarded-Proto` and `X-Forwarded-For` headers set by a known and trusted proxy to make `client` and `scheme` reference the connecting client (shipped with Uvicorn).
 
 ## Real-time web