add utm parameter to links

Author: daGscheid

docs/00-intro.md

@@ -28,8 +28,9 @@ Stereum simplifies the complexity of running Ethereum nodes, making it accessibl
 The Stereum project thrives on community feedback and contributions. We welcome you to join our efforts in making Ethereum more decentralized and accessible:
 
 - **Stereum Websites**: 
-  - [stereum.com](https://stereum.com/) 
-  - [stereum.net](https://stereum.net/)
+  - [stereum.com](https://stereum.com/?utm_source=stereum-documentation&utm_medium=intro-link&utm_id=0) 
+  - [stereum.net](https://stereum.net/?utm_source=stereum-documentation&utm_medium=intro-link&utm_id=0)
+  - [stereumplus.com](https://stereumplus.com/?utm_source=stereum-documentation&utm_medium=intro-link&utm_id=0)
 - **GitHub Repository**: [stereum-dev/ethereum-node](https://github.com/stereum-dev/ethereum-node)
 - **Discord Server**: [Stereum Server](https://discord.gg/DzAwgnSXtB)