ci(renovate): switch to shared configs (#20)

Reviewed-on: #20
Co-authored-by: Timo Behrendt <t.behrendt@t00n.de>
Co-committed-by: Timo Behrendt <t.behrendt@t00n.de>

renovate.json

@@ -1,3 +1,7 @@
 {
-  "$schema": "https://docs.renovatebot.com/renovate-schema.json"
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+  "extends": [
+    "local>t.behrendt/renovate-configs:common",
+    "local>t.behrendt/renovate-configs:action"
+  ]
 }