Custom scaffolder action to allow service integrations to third party services

[t1agob]

Is your feature request related to a problem? Please describe.
The problem that I am trying to solve is of new service onboarding, i.e. when a new service gets created, I want to create a new PD service for it based on the PD team provided by user input.

Describe the solution you'd like
Create scaffolder action to create integrations on a PagerDuty Service from Backstage:

• pagerduty:integrate:*- which integrates the pagerduty service with the other third party services like Datadog, signalFX

Additional context
Original issue raised by @Alok650 in PagerDuty/backstage-plugin#35. Broken down into two issues to reduce scope.