Add XRPL Commons Bootstrap Cluster (hub.xrpl-commons.org)

[Tokeiito]

This pull request adds hub.xrpl-commons.org as a new Bootstrap Cluster in the rippled configuration. XRPL Commons is already well-known within the XRPL community for its educational resources and infrastructure contributions (e.g., UNL Validator, Testnet validator, private ledger for testing testing). We have been considering running a bootstrap cluster for at least a year, and after three months of active work, we are ready to propose this addition.

Details:

Infrastructure Setup:
    The cluster is hosted on dedicated hardware in European data centers.
    Currently consists of four nodes, each behind a load balancer with active health checks.
    Each node accepts up to 400 peers (subject to adjustment based on future demand).
    The setup is designed for easy scalability—up or down—depending on usage requirements.
Minimal History & Peering Only:
    The cluster is configured to store only the bare minimum of ledger history.
    It is dedicated to peering, ensuring efficient and stable connectivity for clients.
Access:
    The Bootstrap Cluster endpoint is: [hub.xrpl-commons.org](https://hub.xrpl-commons.org/)

We appreciate your review and consideration of our request to include this new bootstrap cluster in the official rippled repository. If you have any questions or require additional details about the infrastructure or operations, please let us know. Thank you!