feat(cli): add devmetrics command to rsk-cli with GitHub + Rootstock insights

[lucifer1017]

Summary

This PR adds a new native CLI command, devmetrics, to rsk-cli for collecting developer and contract-level metrics in a single workflow.

It integrates:

• GitHub metrics (repository activity and contributor-related signals)
• Rootstock contract metrics (network-aware on-chain insights)
• Multiple output formats for different use cases: table, json, and markdown
• CI-friendly mode (--ci) for automation pipelines

What was added

• New command: rsk-cli devmetrics
• Repeatable input flags:
  • --repo (repeatable)
  • --contract (repeatable)
• Modular implementation under src/devmetrics/:
  • validation
  • services (github and rootstock)
  • formatters (table, json, markdown)
  • shared types
• Command wiring in bin/index.ts to keep behavior consistent with existing CLI command patterns

Implementation notes

• Rootstock integration is implemented using the existing stack approach (viem) for safer compatibility.
• Validation and error handling were added for malformed/missing inputs and mismatch scenarios.
• The command is designed to be additive and non-breaking to existing rsk-cli functionality.

Usage examples

# Table output
rsk-cli devmetrics --repo owner/repo --contract 0x... --network mainnet --format table

# JSON output
rsk-cli devmetrics --repo owner/repo --contract 0x... --network testnet --format json

# CI mode
rsk-cli devmetrics --repo owner/repo --contract 0x... --ci