Hooks for start/end of scenario

[vorner]

Reading through the cucumber documentation, I glimpsed there should be a way to hook into start/end of a scenario. I didn't find a way to do that as part of this crate.

The ability seems useful ‒ I might want to do some tear-down or cleanup before running the scenarios, so they don't mess with each other (eg. start a fresh docker for each scenario to run in, and stop it once the scenario is finished, or deleting temporary files when done).

What would be a good place to add it?