Update docs

Author: corona10

Doc/library/stdtypes.rst

@@ -5871,6 +5871,16 @@ Frozen dictionaries
    :class:`!frozendict` is not a :class:`!dict` subclass but inherits directly
    from ``object``.
 
+   .. classmethod:: fromkeys(iterable, value=None, /)
+
+      Create a new frozen dictionary with keys from *iterable* and values set to
+      *value*.
+
+      :meth:`fromkeys` is a class method that returns a new frozen dictionary.
+      *value* defaults to ``None``.  All of the values refer to just a single
+      instance, so it generally doesn't make sense for *value* to be a mutable
+      object such as an empty list.
+
    .. versionadded:: next