set default branch of new repo in animint2pages

[tdhock]

hi @Faye-yufan after using animint2pages for a while I noticed that there is a small usability concern. the default branch in new data viz repos is "main" but that is not actually used for anything. only the "gh-pages" branch is used. So it would be good if we could designate "gh-pages" as the default branch, which is possible on the command line via

git branch -M gh-pages

is it possible in gert / animint2pages? That would make it easier for users, which have main as the default branch when they clone (but gh-pages as default would be more user-friendly, so the user would not have to run git branch gh-pages manually).