Document how to generate ENRs using different setups such as Docker and DAppNode

[boulder225]

🎯 Problem to be solved

The documentation at https://docs.obol.tech/docs/start/quickstart_group#step-1-generate-an-enr lacks clear, tabbed instructions for generating or obtaining ENRs using different setups such as Docker and DAppNode.

🛠️ Proposed solution

• [ ] Add a tab in the documentation section to separate the instructions for Docker and DAppNode.
• [ ] Ensure each tab includes step-by-step guidance
• [ ] Include example commands and expected outputs for each method