Modify rule S117: Add exception to kubernetes language

rules/S117/kubernetes/rule.adoc

@@ -4,10 +4,22 @@
 :identifier_or: local variable or function parameter
 :regex: ^[a-z][a-zA-Z0-9]*$
 
-include::../rule.adoc[]
+
+include::../introduction.adoc[]
+
+include::../why-is-this-an-issue.adoc[]
+
+=== Exceptions
+
+The rule does not raise an issue on the usage of the blank identifier `_`.
+
+include::../what-is-the-potential-impact.adoc[]
+
+include::../how-to-fix-it.adoc[]
 
 As a default, we suggest using the camelCase naming convention, as this is widely adopted for variables in Helm.
 
+
 === Code examples
 
 ==== Noncompliant code example
@@ -51,6 +63,11 @@ data:
   {{ $keyC }}: {{ $valC | quote }}
   {{- end }}
 ----
+
+[source,text]
+----
+{{- $_ := set .Values.ingress.annotations "kubernetes.io/ingress.class" .Values.ingress.className -}}
+----
 == Resources
 
 === Documentation