Deploy to heroku fails

[franc014]

• System Information

  • Browser type and version: Chrome 81.0.4044.138 (Official Build) (64-bit)
  • OS type and version: Mac Os Mojave 10.14.16
  • Node version: 12.16.3

• Describe the bug

Hi,
I'm following the instructions from the course in the video https://frontendmasters.com/courses/modern-seo/challenge-1-solution
where we deploy the app to heroku, but after git push origin master completes, it shows an error that says a node version isn't specified in package.json

• To Reproduce
  Steps to reproduce the behavior:

1. Clone the repo
2. cd into modern-seo directory, master branch
3. Add app to heroku: heroku apps:create
4. Add environment variables: heroku config:set EXERCISE=deploy USE_HTTPS=true
5. deploy: git push heroku master

• Expected behavior
  App should be deployed to Heroku

• Screenshots (optional)