feat: add renovate-bot cronjob

- Add new Kubernetes manifests for `renovate-bot` in `k8s-manifests/` directory
  - The Kubernetes manifests include a ConfigMap for `renovate-bot` configuration and a CronJob definition
  - The `renovate-bot` now runs as a Kubernetes CronJob scheduled daily
- Add new `start_renovate_bot.sh` script in `bin/` directory for manual job creation
- Update README and add new README.renovate

🤖

k8s-manifests/renovate-bot.jsonnet

@@ -0,0 +1,27 @@
+local app = import "../_templates/argocd_app.libsonnet";
+
+[
+app + {
+  chart:: "renovate",
+  repo:: "https://docs.renovatebot.com/helm-charts",
+  version:: "36.*",
+  values:: |||
+    fullnameOverride: "renovate-bot"
+    cronjob:
+      schedule: '@daily'
+      concurrencyPolicy: "Forbid"
+    existingSecret: "renovate-env"
+    renovate:
+      persistence:
+        cache:
+          enabled: true
+          storageSize: "128Mi"
+      config: |
+        {
+          "onboardingConfigFileName": ".renovaterc.json",
+          "onboardingConfig": {"extends":["local>infrastructure/renovate-config"]},
+          "autodiscover": true
+        }
+  |||
+}
+]