Updated v3 release notes (markdown)

v3-release-notes.md

@@ -61,22 +61,21 @@ assert result.data["color"] == "RED"
 
 ⚠️ This is a breaking change. You will need to update any resolvers or mutations that accept enums as inputs to support this change. ⚠️ 
 
-Ref: https://github.com/graphql-python/graphene/pull/1153
-
-### Fast ObjectType creation
-
-TODO
-
-### Base64 scalar 
-
-TODO
+Reference: https://github.com/graphql-python/graphene/pull/1153
 
 ### Subscription support
 
 TODO
 
+### 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).
+
+More info here: https://github.com/graphql-python/graphene/pull/1157
+
 ### Other new features
 
+* Add a new Base64 scalar type (https://github.com/graphql-python/graphene/pull/1221)
 * Better error messages when relay `global_id` fails to parse (https://github.com/graphql-python/graphene/pull/1074)
 * Graphene now accepts plain GraphQL types as well as Graphene types (https://github.com/graphql-python/graphene/pull/1224)
 
@@ -123,6 +122,42 @@ result = schema.execute("query { color(colorInput: RED) }")
 assert result.data["color"] == "EnumMeta.RED"
 ```
 
+### ObjectType private fields
+
+Previously you ObjectType's could be initialized with private variables by prepending the variable name with an `_`. This is no longer possible in v3 without defining a custom `__init__` function on the `ObjectType`.
+
+Before:
+
+```python
+from graphene import ObjectType, String
+
+class User(ObjectType):
+    _private_state = None
+
+    name = String()
+
+user = User(name="Leia", _private_state="Extra info")
+assert user._private_state == "Extra info"
+```
+
+After:
+
+```python
+from graphene import ObjectType, String
+
+class User(ObjectType):
+    def __init__(self, _private_state=None, **kwargs):
+        self._private_state = _private_state
+        super().__init__(**kwargs)
+
+    _private_state = None
+
+    name = String()
+
+user = User(name="Leia", _private_state="Extra info")
+assert user._private_state == "Extra info"
+```
+
 ---
 
 A huge thanks to everyone involved in bringing this release together!