Add CAPI Oracle Cloud Infrastructure (OCI) slack channel

Author: joekr

communication/slack-config/channels.yaml

@@ -56,6 +56,7 @@ channels:
   - name: cluster-api-kubemark
   - name: cluster-api-kubevirt
   - name: cluster-api-nested
+  - name: cluster-api-oci
   - name: cluster-api-openstack
   - name: cluster-api-operator
   - name: cluster-api-packet