Added link

Linked "a valid epoch timestamp" to the "Required key-value pairs" section where the timestamp key is described in details.

Author: sujitnewrelic

src/content/docs/data-apis/ingest-apis/metric-api/report-metrics-metric-api.mdx

@@ -28,7 +28,7 @@ Follow this example to send your first metric data points to New Relic:
 
 1. Get the <InlinePopover type="licenseKey"/> for the account you want to report data to.
 2. Insert the license key into the following JSON, and then send the JSON to our [endpoint](#api-endpoint).
-3. Update the `timestamp` value from `CURRENT_TIMESTAMP` to a valid epoch timestamp.
+3. Update the `timestamp` value from `CURRENT_TIMESTAMP` to [a valid epoch timestamp](#json-payload-keys).
    This example creates a single metric data point for a metric named `memory.heap`, but you can create additional attributes or data points by specifying [metric types](/docs/telemetry-data-platform/ingest-manage-data/understand-data/metric-data-type) or adding [optional `common` blocks](#optional-map-attributes).
 
    ```bash