[Notifier][FakeChat] add docs

Author: OskarStark

notifier.rst

@@ -152,6 +152,7 @@ integration with these chat services:
 Service     Package                           DSN
 ==========  ================================  ===========================================================================
 Discord     ``symfony/discord-notifier``      ``discord://TOKEN@default?webhook_id=ID``
+FakeChat    ``symfony/fake-chat-notifier``    ``fakechat+email://MAILER_SERVICE_ID?to=TO&from=FROM``
 Firebase    ``symfony/firebase-notifier``     ``firebase://USERNAME:PASSWORD@default``
 Gitter      ``symfony/gitter-notifier``       ``GITTER_DSN=gitter://TOKEN@default?room_id=ROOM_ID``
 GoogleChat  ``symfony/google-chat-notifier``  ``googlechat://ACCESS_KEY:ACCESS_TOKEN@default/SPACE?thread_key=THREAD_KEY``
@@ -177,7 +178,7 @@ Zulip       ``symfony/zulip-notifier``        ``zulip://EMAIL:TOKEN@HOST?channel
 
 .. versionadded:: 5.3
 
-    The Gitter and Mercure integrations were introduced in Symfony 5.3.
+    The Gitter, Mercure and FakeChat integrations were introduced in Symfony 5.3.
 
 Chatters are configured using the ``chatter_transports`` setting: