communication/slack-config/channels.yaml: Add prometheus-operator-dev

This allows developers and maintainers to communicate in an open channel,
and the current prometheus-operator is left for user questions and
support.

Author: lilic

communication/slack-config/channels.yaml

@@ -281,6 +281,7 @@ channels:
   - name: pr-reviews
   - name: prometheus
   - name: prometheus-operator
+  - name: prometheus-operator-dev
   - name: prow
   - name: prow-alerts
   - name: pt_br-users