Added link to AWS SNS forwarder in integrations docs. (#1184)

* Added link to AWS SNS forwarder in integrations docs.
Signed-off-by: Grodzki Olgierd <olgierd.grodzki@gmail.com>

* Moved AWS SNS forwarder to top of the list.
Signed-off-by: Grodzki Olgierd <olgierd.grodzki@gmail.com>

content/docs/operating/integrations.md

@@ -52,6 +52,7 @@ data volumes.
 For notification mechanisms not natively supported by the Alertmanager, the
 [webhook receiver](/docs/alerting/configuration/#webhook_config) allows for integration.
 
+  * [AWS SNS](https://github.com/DataReply/alertmanager-sns-forwarder)
   * [DingTalk](https://github.com/timonwong/prometheus-webhook-dingtalk)
   * [IRC Bot](https://github.com/multimfi/bot)
   * [JIRAlert](https://github.com/free/jiralert)