README.md needs to be updated.

[aarona]

In the "Quick Start" section before you push the initial changes to heroku for the first time, you need to have a yarn.lock file included in the project. The build fails and suggests running the following commands before doing this:

yarn install
git add yarn.lock
git commit -m "Updated Yarn lockfile"
git push heroku master

[mars]

Thanks for mentioning this, but the instructions are for usingnpm not yarn.

We currently assume that Yarn is a non-standard tooling choice. So it’s up to the developer such as yourself to swap it in where it’s needed.

[aarona]

Got it! Good to know.