User testing guide

[billbrod]

We should write information for user testers:

• Add section to CONTRIBUTING to instruct people on being user testers: how to create the environment from the proper branch, what kind of feedback we'd like, etc
• Add an issue template (or discussion template?) for giving user testing feedback?
  • Instead of this, we could create a dedicated discussion topic for user testing and create a new discussion for feature we want feedback on. Then that discussion would have a template for the testers to copy and fill out, and all feedback happens in a single discussion. Probably works better that way, so it's easier for different testers to see what the others have said and easier for us to collate feedback.

Question to consider:

• Should we have user-testers set up a local environment, or just create a binder for them to use? We won't want that link to be public though.