doc: add comments for #validateEmfTimestamp inside setTimestamp function

Author: arnabrahman

packages/metrics/src/Metrics.ts

@@ -587,6 +587,13 @@ class Metrics extends Utility implements MetricsInterface {
    * @param timestamp - The timestamp to set, which can be a number or a Date object.
    */
   public setTimestamp(timestamp: number | Date): void {
+    /**
+     * The timestamp must be a Date object or an integer representing an epoch time.
+     * This should not exceed 14 days in the past or be more than 2 hours in the future.
+     * Any metrics failing to meet this criteria will be skipped by Amazon CloudWatch.
+     * See: https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/CloudWatch_Embedded_Metric_Format_Specification.html
+     * See: https://docs.aws.amazon.com/AmazonCloudWatch/latest/logs/CloudWatch-Logs-Monitoring-CloudWatch-Metrics.html
+     **/
     if (!this.#validateEmfTimestamp(timestamp)) {
       this.#logger.warn(
         "This metric doesn't meet the requirements and will be skipped by Amazon CloudWatch. " +