document twisted support

Author: altendky

setup.py

@@ -19,6 +19,7 @@
         "async",
         "trio",
         "asyncio",
+        "twisted",
     ],
     extras_require={":python_version < '3.7'": ["contextvars>=2.1"]},
     python_requires=">=3.5",
@@ -28,6 +29,7 @@
         "License :: OSI Approved :: Apache Software License",
         "Framework :: Trio",
         "Framework :: AsyncIO",
+        "Framework :: Twisted",
         "Operating System :: POSIX :: Linux",
         "Operating System :: MacOS :: MacOS X",
         "Operating System :: Microsoft :: Windows",

sniffio/_impl.py

@@ -23,6 +23,8 @@ def current_async_library():
     **asyncio**                      ``"asyncio"``
     **Trio-asyncio**    v0.8.2+     ``"trio"`` or ``"asyncio"``,
                                     depending on current mode
+    **Twisted**         v?+          ``"twisted"`` or ``"asyncio"``,
+                                    depending on current mode
     ================   ===========  ============================
 
     Returns: