Add custom managers to renovate.json for Docker image updates

renovate.json

@@ -1,3 +1,15 @@
 {
-  "$schema": "https://docs.renovatebot.com/renovate-schema.json"
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+  "extends": ["config:recommended"],
+  "customManagers": [
+    {
+      "description": "Update Docker image tags in Nomad job files",
+      "customType": "regex",
+      "fileMatch": ["\\.nomad\\.hcl$"],
+      "matchStrings": [
+        "image\\s*=\\s*\"(?<depName>[^:\"]+):(?<currentValue>[^\"]+)\""
+      ],
+      "datasourceTemplate": "docker"
+    }
+  ]
 }