add git churn alias
add git churn alias

taken from https://github.com/mlafeldt/dotfiles/commit/4fbca97cd1f4241cb477f3ec56e7712905aef85f

bbtb1982/dotfiles,dyong0/dotfiles,abhisood/dotfiles,fieteboerner/dotfiles,jbargu/dotfiles,NerdPad/dotfiles,pekosi/dotfiles,jbargu/dotfiles,OctavianRotari/dotfiles,zhenglaizhang/dotfiles-1,Jooho/dotfiles_mac,joeandrews/dotfiles,jacobxk/dotfiles-1,nicknisi/dotfiles,damca/dotfiles-ubuntu,patnolanireland/dotfiles,jacobxk/dotfiles-1,zhenglaizhang/dotfiles-1,ptgamr/dotfiles,fieteboerner/dotfiles,patnolanireland/dotfiles,nicknisi/dotfiles,ptgamr/dotfiles,OctavianRotari/dotfiles,Jooho/dotfiles_mac,neutrinog/dotfiles,SlyDen/dotfiles,nicknisi/dotfiles,Boukefalos/dotfiles,damca/dotfiles-ubuntu,fieteboerner/dotfiles,paulhirschi/dotfiles,Reesi82/dotfiles,gblock0/dotfiles_unstable,pekosi/dotfiles,bbtb1982/dotfiles