Update channels.yaml

This commit adds a new channel: kubeslice

KubeSlice https://github.com/kubeslice is a new project and has contributors from the community.

We want to encourage the community to participate more in the development of kubeslice, so we would like to move all our discussions to Kubernetes kubeslice open slack channel.

communication/slack-config/channels.yaml

@@ -249,6 +249,7 @@ channels:
   - name: kubernetes-streaming
   - name: kubernetes-teachers
   - name: kubernetes-users
+  - name: kubeslice
   - name: kubespray
   - name: kubespray-dev
   - name: kubevirt-dev