Set up Renovate configuration with default and Docker-specific presets. Updated bot settings and added README.

default.json

@@ -0,0 +1,19 @@
+{
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
+  "description": "Base configuration with standard rules",
+  "extends": [
+    "config:recommended",
+    ":dependencyDashboard",
+    ":separateMajorReleases",
+    ":combinePatchMinorReleases",
+    "group:allNonMajor"
+  ],
+  "packageRules": [
+    {
+      "matchUpdateTypes": ["minor", "patch", "pin", "digest"],
+      "automerge": true,
+      "automergeType": "pr",
+      "platformAutomerge": true
+    }
+  ]
+}