I wanted to find my github website using regular expressions. anyway, maybe?
AFAIK you will need to configure this yourself. Github has its own search syntax with qualifiers that you can add, but not with a full regex. Api uses the same syntax as browser searches.
The problem is that GitHub searches are limited to the master branch of your repos.
master
The simplest solution:
git grep
git grep -E
git log --all -S...
git rev-list --all|grep xxx