fix extras APNS_ASYNC -> apns-async

to conform with Core metadata specification https://packaging.python.org/en/latest/specifications/core-metadata/#provides-extra-multiple-use

README.rst

@@ -37,7 +37,7 @@ Dependencies
 - For WebPush (WP), pywebpush 1.3.0+ is required (optional). py-vapid 1.3.0+ is required for generating the WebPush private key; however this
   step does not need to occur on the application server.
 - For Apple Push (APNS), apns2 0.3+ is required (optional).
-- For Apple Push (APNS_ASYNC) using async, aioapns 3.1+ is required (optional). Installed aioapns overrides apns2 which does not support python 3.10+.
+- For Apple Push (apns-async) using async, aioapns 3.1+ is required (optional). Installed aioapns overrides apns2 which does not support python 3.10+.
 - For FCM, firebase-admin 6.2+ is required (optional).
 
 Setup
@@ -46,7 +46,7 @@ You can install the library directly from pypi using pip:
 
 .. code-block:: shell
 
-	$ pip install django-push-notifications[WP,APNS_ASYNC,FCM]
+	$ pip install django-push-notifications[WP,apns-async,FCM]
 
 
 Edit your settings.py file:

setup.cfg

@@ -43,7 +43,7 @@ APNS =
 
 WP = pywebpush>=1.3.0
 
-APNS_ASYNC = aioapns>=3.1
+apns-async = aioapns>=3.1
 
 FCM = firebase-admin>=6.2