Set __module__ = 'httpx' on everything we expose via the public API. (#1155)

* Set __module__='httpx' on everything we expose via the public API

* Linting

* Update httpx/__init__.py

* Update httpx/__init__.py

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

Author: lovelydinosaur

httpx/__init__.py

@@ -109,3 +109,9 @@
     "DigestAuth",
     "WSGITransport",
 ]
+
+
+_locals = locals()
+for name in __all__:
+    if not name.startswith("__"):
+        setattr(_locals[name], "__module__", "httpx")  # noqa