Add repeat handling documentation (#319)

- Repeat handling was not described in backend. Added a link to information about it in the frontend.

Author: erik-edling

wiki/markdown/subscriptions.md

@@ -123,4 +123,7 @@ our condition:
     confidenceLevels[?name=='dummy_1_stable'] && confidenceLevels[?value=='SUCCESS']
 
 These two conditions check both that the artifact name is the right one,
-and that the confidence level is what we are looking for.
+and that the confidence level is what we are looking for.
+
+### Repeat handling
+See in the frontend documentation [here](https://github.com/eiffel-community/eiffel-intelligence-frontend/blob/master/wiki/markdown/add-subscription.md)