[DOCS] Adds OpenTelemetry docs to index

Author: picandocodigo

docs/integrations.asciidoc

@@ -6,6 +6,7 @@ the Ruby client.
 
 * <<transport>>
 * <<api>>
+* <<opentelemetry>>
 * <<ecs>>
 * <<activemodel_activerecord>>
 * <<ruby_on_rails>>
@@ -16,6 +17,8 @@ include::transport.asciidoc[]
 
 include::api.asciidoc[]
 
+include::open-telemetry.asciidoc[]
+
 include::ecs.asciidoc[]
 
 include::model.asciidoc[]