Run action on Node.js 16

Node.js 12 actions are deprecated, so this is a required upgrade.

Add check for blank custom change event summaries.

Merge pull request #10 from tanguyantoine/patch-1

fix: ensure customEvent is not empty

Add support for custom change event summaries.

Thanks to @stempler for the contribution!

v1.0.0

PagerDuty recently released a new feature for tracking changes to your services. Change events represent service changes such as deploys, build completion, configuration updates, etc., providing contextual information that is critical during incident triage or. See https://support.pagerduty.com/docs/change-events for more information.