Heroku "staging" instance

[mariekers]

Set master branch up against heroku as a POC for orgs that want to make their own instance and to ensure tool still works on heroku

[lottspot]

We discussed this a little bit on slack; reiterating some of the takeaways here:

• GH Actions may have some integrated Heroku actions. We should look into this.
• We will need Heroku credentials to give the CI runner access to a non-prod project to deploy to

[mariekers]

@lottspot guessing this is done?

[lottspot]

Not yet, sorry... should be able to complete it this morning

[lottspot]

Pending review in #144