expand upon example of using an index as a metric_tag (#12438)
expand upon example of using an index as a metric_tag (#12438)

Co-authored-by: Heston Hoffman <2660ee083f24c195d9ec13293b4e79445cc456e2@gmail.com>
Co-authored-by: Florian Veaux <e7f01e0bc37726d2ca18b651dc6e7b02e4ad2678@datadoghq.com>
DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core,DataDog/integrations-core