Do you mean the button on the Web App, or on the main HTTP panel?
We could try to add this on the Web App, but from what I remember this is a bit problematic due to CORS . On the other hand, without the Web App it's also a bit hard, because Github only provides binaries over HTTPS, it doesn't support HTTP itself, and this would mean that OBK would have to have HTTPS always built in. You could also have your own update server with HTTP, only then this server would in turn have to download the binary files from Github and would have to be constantly available on the network.