Add github workflow to test `server.js`

[Maxime Chevalier-Boisvert]

Since we're actively making changes to the server, I think it might make sense to add a GitHub CI workflow to test it.

Something like:

• Install the dependencies
• Check that we can start the server
• Do some simple requests using wget, at least make sure we can get /, /help, /browse without crashing

Help setting this up would be most welcome :)