doc: add security incident reponse plan

doc: add security incident reponse plan · nodejs/node@1784c35

Original file line number	Diff line number	Diff line change
`@@ -284,3 +284,8 @@ Security notifications will be distributed via the following methods.`
`284`	`284`	`If you have suggestions on how this process could be improved, please visit`
`285`	`285`	`the [nodejs/security-wg](https://github.com/nodejs/security-wg)`
`286`	`286`	`repository.`
	`287`	`+`
	`288`	`+## Incident Response Plan`
	`289`	`+`
	`290`	`+In the event of a security incident, please refer to the`
	`291`	`+[Security Incident Response Plan](https://github.com/nodejs/security-wg/blob/main/INCIDENT_RESPONSE_PLAN.md).`