chore: configure Renovate (#141)

Configure renovate to update the Debian images used as base for the
minimal and standard container images.

Signed-off-by: Francesco Canovai <francesco.canovai@enterprisedb.com>
Co-authored-by: Francesco Canovai <francesco.canovai@enterprisedb.com>

renovate.json

@@ -0,0 +1,21 @@
+{
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+  "extends": ["config:recommended", "docker:pinDigests"],
+  "enabledManagers": ["custom.regex"],
+  "customManagers": [
+    {
+      "customType": "regex",
+      "fileMatch": ["docker-bake.hcl"],
+      "matchStrings": [
+        "\\/\\/\\s*renovate:\\s*datasource=(?<datasource>.*?)\\s+(versioning=(?<versioning>.*?))?\\s+\"(?<depName>[^:]+):(?<currentValue>[^\\s@]+)(@(?<currentDigest>sha256:[0-9a-f]*))?\""
+      ],
+      "versioningTemplate": "{{#if versioning}}{{{versioning}}}{{else}}semver{{/if}}"
+    }
+  ],
+  "packageRules": [
+    {
+      "matchPackageNames": ["debian"],
+      "groupName": "Debian base images"
+    }
+  ]
+}