docs: add new metric ingress_controller_admission_count

Author: dweber019

app/_src/kubernetes-ingress-controller/production/observability/prometheus.md

@@ -72,6 +72,17 @@ This metric provides these labels:
 
 `ingress_controller_translation_broken_resource_count` (type: `gauge`) provides the number of resources that the controller cannot successfully translate to {{site.base_gateway}} configuration.
 
+{% endif_version %}
+{% if_version gte:3.2.x %}
+### ingress_controller_admission_count
+
+`ingress_controller_admission_count` (type: `counter`) provides the number of admissions that the admission webhook processes.
+
+This metric provides these labels:
+
+* `allowed` describes whether an admission was allowed
+* `resource` describes the resource under admission
+
 {% endif_version %}
 
 ## Low-level performance metrics