This gist contains a script for cloning all the extensions in the current directory. I recommend following the current steps, however you are free to clone these anywhere.
cd ~/Source
mkdir auth0-extensions && cd "$_"
curl https://gist.githubusercontent.com/sgmeyer/f622dd49e661c4b62e447530af2762b8/raw/c39122d57cf3ae41b6fd17019432b48edb8415e0/checkout-all-repos.sh" > checkout-all-repos.sh
bash checkout-all-repos.sh
Note: This script expects you to have SSH access to GitHub. It will fail if you do not have this setup. Be sure