ci: add Renovate config (#802)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: Shohei Ueda <30958501+peaceiris@users.noreply.github.com>

renovate.json

@@ -0,0 +1,9 @@
+{
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+  "extends": [
+    "local>peaceiris/renovate-config"
+  ],
+  "enabledManagers": [
+    "nvm"
+  ]
+}