Add version changed indicators to Enum members

The Enum members listed in the sections of `__dunder__` and `_sunder_`
did not have version indicators in the API docs.
This changes adds the version indicators mentioned in the  `__dunder__`
and `_sunder_` section to the corresponding Enum member.

Author: RafaelWO

Doc/library/enum.rst

@@ -321,6 +321,8 @@ Data Types
          In Python 2 code the :attr:`~Enum._order_` attribute is necessary as definition
          order is lost before it can be recorded.
 
+      .. versionadded:: 3.6
+
    .. attribute:: Enum._ignore_
 
       ``_ignore_`` is only used during creation and is removed from the
@@ -330,6 +332,8 @@ Data Types
       names will also be removed from the completed enumeration.  See
       :ref:`TimePeriod <enum-time-period>` for an example.
 
+      .. versionadded:: 3.7
+
    .. method:: Enum.__dir__(self)
 
       Returns ``['__class__', '__doc__', '__module__', 'name', 'value']`` and
@@ -372,6 +376,10 @@ Data Types
          >>> PowersOfThree.SECOND.value
          9
 
+      .. versionadded:: 3.6
+      .. versionchanged:: 3.13
+         Prior versions would use the last seen value instead of the highest value.
+
    .. method:: Enum.__init__(self, *args, **kwds)
 
       By default, does nothing.  If multiple values are given in the member
@@ -410,6 +418,8 @@ Data Types
          >>> Build('deBUG')
          <Build.DEBUG: 'debug'>
 
+      .. versionadded:: 3.6
+
    .. method:: Enum.__new__(cls, *args, **kwds)
 
       By default, doesn't exist.  If specified, either in the enum class