feat: add docker-proxy-config troubleshooting lab

[HimanM]

Description

This PR adds a new troubleshooting lab where users diagnose why Docker pulls fail behind a corporate proxy and learn how to configure the Docker daemon proxy settings.

Type of change

• Bug fix
• New feature
• New Lab

Lab Requirements (If submitting a new lab)

• The \lab.yaml\ is fully populated.
• The \cloud-init.yaml\ correctly breaks the environment.
• The \�erify.sh\ script correctly asserts if the environment is fixed.
• The \solution.md\ provides the step-by-step solution to fix the environment.
• The \question.md\ provides the question for the lab.
• Follows the LAB_FORMAT.md guidelines.
• MANDATORY: A working \solution.sh\ script is provided to automatically fix the environment.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code

Closes Issues ?

• closes issue [LAB IDEA] Docker Pull Fails Behind Corporate Proxy #84