Updated v3 release notes (markdown)

v3-release-notes.md

@@ -63,6 +63,36 @@ assert result.data["color"] == "RED"
 
 Reference: https://github.com/graphql-python/graphene/pull/1153
 
+### Subscription support	
+
+Graphene v3 add subscription support 🎉 Here is an example of it in action:
+
+```python
+from graphene import ObjectType, Int, Schema
+
+class Subscription(ObjectType):
+    count_to_ten = Int()
+
+    async def subscribe_count_to_ten(root, info):
+        count = 0
+        while count < 10:
+            count += 1
+            yield count
+
+class Query(ObjectType):
+    a = String()
+
+schema = Schema(query=Query, subscription=Subscription)
+
+result = await schema.subscribe("subscription { countToTen }")
+count = 0
+async for item in result:
+    count = item.data["countToTen"]
+assert count == 10
+```
+
+**Note:** Using subscriptions with a server like Django or Flask still relies on the server supporting websockets.
+
 ### Fast ObjectType creation
 
 In Graphene v3 optimises the ObjectType initialization resulting in a x3 speed up! It does this by leveraging the same strategy that dataclasses introduced (dynamic creation of optimal `__init__` functions based on eval).