Add integration for Reqnroll

[craigfowler]

SpecFlow is dead! It has been fully withdrawn, but there is an active fork named Reqnroll: https://reqnroll.net/news/2024/02/from-specflow-to-reqnroll-why-and-how/

A new integration needs to be created, and the SpecFlow one retired.

[craigfowler]

I'm fairly sure I can do this by using the same code twice and just switching namespaces.