Crosslink Puma docs

doc/administration/monitoring/prometheus/puma_exporter.md

@@ -25,3 +25,5 @@ To enable the Puma exporter:
    for the changes to take effect.
 
 Prometheus begins collecting performance data from the Puma exporter exposed at `localhost:8083`.
+
+For more information on using Puma with GitLab, see [Puma](../../operations/puma.md).

doc/administration/operations/puma.md

@@ -224,3 +224,8 @@ in Puma when using the Linux package, and which ones have no corresponding count
 | `unicorn['exporter_enabled']`        | `puma['exporter_enabled']`         |
 | `unicorn['exporter_address']`        | `puma['exporter_address']`         |
 | `unicorn['exporter_port']`           | `puma['exporter_port']`            |
+
+## Puma exporter
+
+You can use the Puma exporter to measure various Puma metrics. For more information, see
+[Puma exporter](../monitoring/prometheus/puma_exporter.md).