Add #openstack-charms to accessbot

Add the channel to accessbot, this is needed so that
statusbot works - see merged change:
https://review.openstack.org/#/c/329159/

Change-Id: Iea6d345c63b54c41bb55a85c6571b0dede2b876a

accessbot/channels.yaml

@@ -90,6 +90,7 @@ channels:
   - name: openstack-blazar
   - name: openstack-board
   - name: openstack-browbeat
+  - name: openstack-charms
   - name: openstack-chef
   - name: openstack-cinder
   - name: openstack-cloudkeep