Add sig-api-machinery-storageversion-dev channel

For discussions around:

kubernetes/enhancements#2339
kubernetes/enhancements#4192

Author: enj

communication/slack-config/channels.yaml

@@ -443,6 +443,7 @@ channels:
   - name: shoutouts
   - name: sig-api-machinery
   - name: sig-api-machinery-cel-dev
+  - name: sig-api-machinery-storageversion-dev
   - name: sig-apps
   - name: sig-auth
   - name: sig-auth-authenticators-dev