Add dropdown to select Escalation Policy

[t1agob]

Is your feature request related to a problem? Please describe.
Currently, when creating a PagerDuty service through the scaffolder action users need to provide the Escalation Policy ID. This requires them to copy the Id from the PagerDuty console. This can be improved.

Describe the solution you'd like
I would like to have a dropdown of all Escalation Policies I have access to and just select the correct one.

Describe alternatives you've considered
Currently the only alternative is to copy the Id from PagerDuty. I don't see other way of achieving it.

[t1agob]

Solved in #6 and merged to main on #7.