new mirror on mirrors.tuna.tsinghua.edu.cn

Thanks to @z4yx we now have a new mirror in China! Anyone can add it by clicking on this link:

https://mirrors.tuna.tsinghua.edu.cn/fdroid/repo?fingerprint=43238D512C1E5EB2D6569F4A3AFBF5523418B82E0A3ED1552770ABB9A9C9CCAB

Its also available via rsync:

rsync -axv mirrors.tuna.tsinghua.edu.cn::fdroid/ /path/to/fdroid/

Its on the mirror monitor mirror-monitor!9 (merged) Once the whole setup proves stable, we can add it as an official mirror.