Enhance bridging information for Brid.gg and Relay

[Elexy101]

Updated Brid.gg section to include bridging options for Sepolia testnet and added Relay information.

What changed? Why?

• Fixed the Brid.gg link to point to the main page (https://brid.gg) instead of a broken subpage so users can properly select their source and destination chains via the interface.
• Added clarification that Brid.gg uses a dropdown selection interface for choosing source/destination chains.
• Added a new Relay bridge section with supported networks:
  Base Mainnet
  Base Sepolia Testnet

The previous Brid.gg documentation had a broken link (page not found) and was missing Base / Base-Sepolia testnet support. This update fixes the link, improves accuracy, and documents the newer Relay bridge option for better developer and user experience

Notes to reviewers

• All links have been verified as functional.

How has it been tested?

• Manually verified all bridge links and flows.

[cb-heimdall]

🟡 Heimdall Review Status

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