added northflank to adopters list
* [Render](https://render.com) uses CoreDNS in production across all its Kubernetes clusters.
* [BackMarket](https://www.backmarket.com) uses CoreDNS within Kubernetes in production, with standard configuration.
* [Absa Group](https://www.absa.africa) uses CoreDNS as an integral part of Kubernetes Global Balancer project - [k8gb](https://www.k8gb.io/).
+* [Northflank](https://northflank.com/) uses CoreDNS on all of our Kubernetes clusters across GCP, AWS, and bare-metal.
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