chore: add renovate regex managers for Dockerfile deps (base image + @openchamber/web)

renovate.json

@@ -0,0 +1,24 @@
+{
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+  "regexManagers": [
+    {
+      "description": "Track openchamber base Docker image FROM jcabillot/opencode",
+      "fileMatch": ["^Dockerfile$"],
+      "matchStrings": [
+        "FROM jcabillot/opencode:(?<currentValue>[^\\s]+)"
+      ],
+      "depNameTemplate": "jcabillot/opencode",
+      "datasourceTemplate": "docker"
+    },
+    {
+      "description": "Track @openchamber/web npm version from ARG in Dockerfile",
+      "fileMatch": ["^Dockerfile$"],
+      "matchStrings": [
+        "ARG OPENCHAMBER_WEB_VERSION=(?<currentValue>[^\\s]+)"
+      ],
+      "depNameTemplate": "@openchamber/web",
+      "datasourceTemplate": "npm",
+      "versioningTemplate": "npm"
+    }
+  ]
+}