documentation for travel timedelta support

HISTORY.rst

@@ -3,6 +3,7 @@ History
 =======
 
 * Build Windows ARM64 wheels.
+* Add support for ``datetime.timedelta`` to ``time_machine.travel()``
 
 2.8.2 (2022-09-29)
 ------------------

README.rst

@@ -80,6 +80,7 @@ It may be:
 * A ``float`` or ``int`` specifying a `Unix timestamp <https://en.m.wikipedia.org/wiki/Unix_time>`__
 * A string, which will be parsed with `dateutil.parse <https://dateutil.readthedocs.io/en/stable/parser.html>`__ and converted to a timestamp.
   Again, if the result is naive, it will be assumed to have the UTC time zone.
+* A ``datetime.timedelta`` relative to the current real time.
 
 .. |zoneinfo-instance| replace:: ``zoneinfo.ZoneInfo`` instance
 .. _zoneinfo-instance: https://docs.python.org/3/library/zoneinfo.html#zoneinfo.ZoneInfo