Inside your server folder, open config.json and add the following line
"allow-cef-debugging": true
Now head to your registry (Windows Key + R ) and type regedit and hit enter. Head to the following path:
Once you're there, right click and Go New > String Value and put "launch.cefPort" as the name and Hit Enter, then right click and hit Modify and set the data to the port you'd like to use (9222 for example) and it should look the same as below
Now head to your browser using the following: http://localhost:9222/ or whatever port you had entered to enable it.
You'll need to quit Rage and open it back up if you enabled this while in game, and make sure you restart your server when you change the setting.
Credits to @kemperrr as I used his post on Discord to make this up.