docs: enhance convert contract readme

[fmorency]

This pull request updates the contracts/converter/README.md documentation to provide comprehensive deployment, interaction, and usage instructions for the Converter contract. The changes make it much easier for users and developers to find contract addresses, interact with the contract on both mainnet and testnet, and understand prerequisites and command usage.

Deployment and interaction documentation:

• Added a "Deployed Contracts" section listing mainnet and testnet contract addresses for quick reference.
• Introduced detailed instructions for interacting with the contract via REST and RPC, including network endpoints, prerequisites for installing manifestd, and base64 encoding for REST queries.

Usage examples:

• Provided step-by-step query and execution examples for common contract operations, including converting tokens, updating config, and transferring admin privileges, with both mainnet and testnet commands.

Reference links:

• Added a direct link to the manifestd repository for easier access to the required chain binary.

[Copilot]

Pull request overview

This PR significantly enhances the Converter contract documentation by adding comprehensive deployment information, interaction guides, and practical usage examples. The changes transform the README from a basic contract description into a complete reference guide for developers and users.

Key Changes:

• Added deployed contract addresses for mainnet and testnet environments
• Introduced detailed interaction instructions for both REST and RPC methods
• Provided step-by-step examples for querying and executing contract operations

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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