Migrate config .github/renovate.json (#686)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

.github/renovate.json

@@ -1,14 +1,21 @@
 {
   "$schema": "https://docs.renovatebot.com/renovate-schema.json",
   "extends": [
-    "config:base",
+    "config:recommended",
     ":semanticCommitsDisabled"
   ],
-  "enabledManagers": ["regex"],
-  "regexManagers": [
+  "enabledManagers": [
+    "custom.regex"
+  ],
+  "customManagers": [
     {
-      "fileMatch": ["src/site/site.xml"],
-      "matchStrings": ["<version>(?<currentValue>.*?)<\/version>"],
+      "customType": "regex",
+      "fileMatch": [
+        "src/site/site.xml"
+      ],
+      "matchStrings": [
+        "<version>(?<currentValue>.*?)</version>"
+      ],
       "depNameTemplate": "org.apache.maven.skins:maven-fluido-skin",
       "datasourceTemplate": "maven"
     }
@@ -17,5 +24,7 @@
     "dependencies"
   ],
   "rebaseWhen": "conflicted",
-  "schedule": ["on the first day of the month"]
+  "schedule": [
+    "on the first day of the month"
+  ]
 }