Only open renovate PRs for LTS Node versions

renovate.json

@@ -14,6 +14,12 @@
         "minor",
         "patch"
       ]
+    },
+    {
+      "matchDatasources": ["docker"],
+      "matchPackageNames": ["node"],
+      "versionCompatibility": "^(?<version>[^-]+)(?<compatibility>-.*)?$",
+      "versioning": "node"
     }
   ]
 }