Add renovate.json (#162)

Co-authored-by: Renovate Bot <bot@renovateapp.com>

Author: renovate[bot]

renovate.json

@@ -0,0 +1,6 @@
+{
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+  "extends": [
+    "local>oxidecomputer/renovate-config"
+  ]
+}