feat-pagerduty - added conversion for pagerduty plugin

[vanisrikanithi]

pagerduty go-conversion:
Added "Pagerduty " support to go-convert specific to jenkins migration.

Pager Duty Jenkins Trace:
test-pager-duty.json

go run main.go jenkinsjson --downgrade ~/go/test-pager-duty.json

pagerduty step:

- step:
    identifier: pagerduty51d22b
    name: Pagerduty
    spec:
      image: plugins/pagerduty
      settings:
        dedup_key: E54EC853A59A3815EF3632D5F854CF26
        incident_severity: critical
        incident_source: test-pager-duty
        incident_summary: Build Failed for test-pager-duty
        job_status: failure
        log_level: debug
        resolve: 'false'
        routing_key: a666ad1326f34605d06c0dbd4d87c1cb
    timeout: ''
    type: Plugin

pagerdutyChangeEvent step:

- step:
    identifier: pagerdutychangeevent499434
    name: Pagerduty_Change_Event
    spec:
      image: plugins/pagerduty
      settings:
        custom_details: '{"buildNumber":"22","jobName":"test-pager-duty","jobURL":"http://localhost:8080/job/test-pager-duty/22/"}'
        incident_source: ''
        incident_summary: Job test-pager-duty completed with status SUCCESS
        log_level: debug
        routing_key: a666ad1326f34605d06c0dbd4d87c1cb
        create_change_event: "true"
    timeout: ''
    type: Plugin

[vanisrikanithi]

@Ompragash Added the pagerduty and pagerdutyChangeEvent support to go-convert, Could you please review it and confirm the changes?

Thanks,