Migration path for AdCodicem's plugin

[mbhoek]

As discussed in #75, the plugin available at https://github.com/AdCodicem/SpecFlowMicrosoftDependencyInjection will no longer be maintained, but it does have a number of features we might want to implement in this plugin and/or provide a migration path.

• IServicesConfigurator pattern (instead of a static class/method)
• AddDelegate feature (instead of the fixed delegates)

[mbhoek]

Closing this issue because the plugin will be donated to Reqnroll.