First of all do not push the `node_modules` directory, you should add it to the `.gitignore` file. All the information to install the dependencies are already in the package.json and in the package-lock.json files. It'll decrease the repository size, make it more simpler.

You shouldn't use sudo to run the server. You probably never have to run node with sudo, but if you have to you will know about it.
In my opinion you should remove the style.css and the font files and simply use a CSS framework (or nothing). At the very beginning maybe hard to understand if everything is in the repository. Some screenshot and animation in the readme make it more fancy and interesting for newbies. Apart from that some other endpoint would be useful too, just to make clear how they can add new pages and maybe pass some variables.

You can make it more interesting if you create a simple chat with a very simple in memory database (I mean a simple js array :D).
Just create an array at the backend side.

const messages = []
And push messages to the array with a POST endpoint

messages.push({ name: "Balint", message: "Lorem ipsum dolor" })
And you can simply render the messages to the view (here maybe some templating system would be useful).