Create new vertical-pod-autoscaler channel

vertical-pod-autoscaler is a big enough subproject in sig-autoscaling
that it needs a dedicated channel.

I also noticed that the karpenter channel wasn't listed, so I added
that.

communication/slack-config/channels.yaml

@@ -548,6 +548,7 @@ channels:
   - name: velero-dev
   - name: velero-users
     id: C6VCGP4MT
+  - name: vertical-pod-autoscaler
   - name: virtlet
   - name: virtual-kubelet
   - name: virtualization

sigs.yaml

@@ -683,9 +683,13 @@ sigs:
     - https://raw.githubusercontent.com/kubernetes/api/master/autoscaling/OWNERS
     - https://raw.githubusercontent.com/kubernetes/kubernetes/master/pkg/controller/podautoscaler/OWNERS
   - name: karpenter
+    contact:
+      slack: karpenter
     owners:
     - https://raw.githubusercontent.com/kubernetes-sigs/karpenter/main/OWNERS
   - name: vertical-pod-autoscaler
+    contact:
+      slack: vertical-pod-autoscaler
     owners:
     - https://raw.githubusercontent.com/kubernetes/autoscaler/master/vertical-pod-autoscaler/OWNERS
 - dir: sig-cli