Doc: Some improvements concern ellipsis into typing doc

Author: adorilson

Doc/library/typing.rst

@@ -230,9 +230,11 @@ For example:
 
    callback: Callable[[str], Awaitable[None]] = on_update
 
+.. index:: single: ...; ellipsis literal
+
 The subscription syntax must always be used with exactly two values: the
 argument list and the return type.  The argument list must be a list of types,
-a :class:`ParamSpec`, :data:`Concatenate`, or an ellipsis. The return type must
+a :class:`ParamSpec`, :data:`Concatenate`, or an ellipsis (``...``). The return type must
 be a single type.
 
 If a literal ellipsis ``...`` is given as the argument list, it indicates that
@@ -375,8 +377,11 @@ accepts *any number* of type arguments::
    # but ``z`` has been assigned to a tuple of length 3
    z: tuple[int] = (1, 2, 3)
 
+.. index:: single: ...; ellipsis literal
+
 To denote a tuple which could be of *any* length, and in which all elements are
-of the same type ``T``, use ``tuple[T, ...]``. To denote an empty tuple, use
+of the same type ``T``, use the literal ellipsis ``...``: ``tuple[T, ...]``.
+To denote an empty tuple, use
 ``tuple[()]``. Using plain ``tuple`` as an annotation is equivalent to using
 ``tuple[Any, ...]``::
 
@@ -1162,6 +1167,8 @@ These can be used as types in annotations. They all support subscription using
 
    Special form for annotating higher-order functions.
 
+   .. index:: single: ...; ellipsis literal
+
    ``Concatenate`` can be used in conjunction with :ref:`Callable <annotating-callables>` and
    :class:`ParamSpec` to annotate a higher-order callable which adds, removes,
    or transforms parameters of another