chore: prevent major bumps to normalize-url

The highest version that can be used in a browser is 4, after which
Safari is likely to break.

renovate.json

@@ -15,6 +15,10 @@
     {
       "groupName": "Monaco Editor",
       "matchPackageNames": ["monaco-editor", "monaco-editor-webpack-plugin"]
+    },
+    {
+      "matchPackageNames": ["normalize-url"],
+      "allowedVersions": "<5.0.0"
     }
   ],
   "ignorePaths": [