add sevensphere as Kamaji Adopter

ADOPTERS.md

@@ -8,6 +8,7 @@ Feel free to open a Pull-Request to get yours listed.
 | Type | Name | Since | Website | Use-Case |
 |:-|:-|:-|:-|:-|
 | End-user | KINX | 2024 | [link](https://kinx.net/?lang=en) | KINX is an Internet infrastructure service provider and will use kamaji for its new [Managed Kubernetes Service](https://kinx.net/service/cloud/kubernetes/intro/?lang=en). |
+| End-user | sevensphere | 2023 | [link](https://www.sevensphere.io) | Sevensphere provides consulting services for end-user companies / cloud providers and uses Kamaji for designing cloud/on-premises Kubernetes-as-a-Service platform. |
 | Vendor | Ænix | 2023 | [link](https://aenix.io/) | Ænix provides consulting services for cloud providers and uses Kamaji for running Kubernetes-as-a-Service in free PaaS platform [Cozystack](https://cozystack.io). |
 | Vendor | Netsons | 2023 | [link](https://www.netsons.com) | Netsons is an Italian hosting and cloud provider and uses Kamaji in its [Managed Kubernetes](https://www.netsons.com/kubernetes) offering. |