e2e testing to improve CI/CD

[tonyketcham]

Is your feature request related to a problem? Please describe. Managing dependency updates ahead of the official Sapper template is not guaranteed to be stable. While a project may successfully build, a major change in a dependency could create breaking changes at runtime.

Describe the solution you'd like Being able to test the core features of Sapper in the context of this biased config with e2e testing would allow dependabot to automatically merge updates with confidence that CircleCI catches breaking changes.