Moving docs to tootsuite/documentation (#1550)

docs/Using-the-API/Push-notifications.md

@@ -1,4 +1 @@
-Push notifications
-==================
-
-See <https://github.com/Gargron/tusky-api> for an example of how to create push notifications for a mobile app. It involves using the Mastodon streaming API on behalf of the app's users, as a sort of proxy.
+[The documentation has moved to its own repository](https://github.com/tootsuite/documentation/blob/master/Using-the-API/Push-notifications.md)