Add note on how to run the ui project in the documentation

[unfilledflag]

Is your enhancement request related to a problem? Please describe.
The docs at this article explain how to build a monorepo on Heroku, but the start process only starts the backend.

Describe the solution you'd like
Add a note on how to start the frontend, or how to link the backend to see it.

Describe alternatives you've considered
I'm using https://medium.com/inato/how-to-setup-heroku-with-yarn-workspaces-d8eac0db0256 this article that requires two separate Heroku instances, each starting a dyno.