if [ -f package-lock.json ]; then
    echo "package-lock.json found, that's bad because we're using Yarn!"
    exit 1;
else
    echo "No package-lock.json found, that's good because we're using Yarn!"
    exit 0;
fi

Add CI script to detect package-lock.json
Add CI script to detect package-lock.json

+ If package-lock.json is present it blocks deploys to Heroku since we're using Yarn and Heroku won't accept a project with both a package-lock.json and a yarn.lock file present
