Right now this project has a lot of technically debt. However it's no dead yet.
If you wish to add a new mirror to the website it's as easy as editing files in pug/. Then run gulp pug and finally ./setup.sh.
The stats page does not have a pug file, so if you wish to change that you will have to write HTML manually. This also implies that the footer with the mirror contacts has to be edit here seperately from include/_footer.pug
Best of luck.