Assuming this isn't snark - because if I am looking for a tool to do a job, seeing an immediate visual representation of what I am likely to expect is very helpful. I don't want to go through the full installation to view a demo and then immediately realise it was not remotely close to what I was expecting.
I also think a screenshot in a README is very helpful, but do note that the demo requires no install. The linked GitHub repository has a homepage set, and it is https://status.harry.id which I think is pretty obviously a demo just from the URL.
Generally I'd agree, but the link he posted is a single click, requires no install, no login, no nothing. Nevertheless, here I took a screenshot for you: https://i.imgur.com/63kPIh9.png
Consider adding a screenshot.