Add servo feedback interface

[Ericsii]

Proposed change(s)

Add servo position and effort feedback API

Useful links (GitHub issues, forum threads, etc.)

Types of change(s)

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code refactor (non-breaking change which refactor the code)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update only
• Other (please describe)

Testing and Verification

Test Configuration

Mini Pupper Version
Mini Pupper 2, Mini Pupper 2 Pro

Raspberry Pi OS + ROS version
Ubuntu 22.04, ROS 2 Humble

PC OS + ROS version
Ubuntu 22.04, ROS 2 Humble

Checklist

• I have read the CONTRIBUTING guidelines.
• I have checked to ensure there aren't other open Pull Requests for the same change.

Other comments