Label the PRs created by Renovate (#883)

This gives us something to filter on

@michaelkedar had this idea while we were walking through the release
process this week.

https://docs.renovatebot.com/configuration-options/#labels

renovate.json

@@ -5,6 +5,7 @@
   ],
   "timezone": "Australia/Sydney",
   "schedule": ["before 6am on monday"],
+  "label": ["dependencies"],
   "packageRules": [
     {
       "matchUpdateTypes": ["major"],