Move cucumber to a dependency instead of a peer dependency

[plocket]

Also, probably remove devDependency of cucumber.

[plocket]

Connected to SuffolkLITLab/docassemble-ALKilnSetup#163

[plocket]

As a discussion, this covers why we're deciding against having puppeteer and cucumber as peer dependencies.

This framework is mostly made for people who aren't familiar with git/github/standard development in general and are focused on developing docassemble interviews. We don't expect them to develop their own puppeteer code or cucumber steps. If users do choose to do those things, then they should use their own versions of those libraries so they aren't dependent on us to keep up to date on their own versions of those libraries. Their work and our work doesn't need to stay aligned.

In the future, we might make better hooks for people to customize our code (for example, with custom fields). At that point we might discuss how to keep versions aligned.

It might be good to add documentation, at some point, for how people can develop on their own and/or diverge from our code.