Revert "test: remove renovate, later re-add it"

renovate.json5

@@ -0,0 +1,12 @@
+{
+    "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+    "extends": [
+        "config:recommended",
+        ":gitSignOff"
+    ],
+    "timezone": "Europe/Berlin",
+    "labels": [
+        "dependencies",
+        "3. to review"
+    ],
+}