Add load balancer tutorial to Go section

[CarlosAlbertoFurtado]

Description

Added a tutorial on building a simple load balancer with Go to the Go section.

Motivation and Context

The Go section has tutorials for web apps, blockchain, chat apps, and REST APIs, but no tutorial covering load balancing — a fundamental concept in backend/infrastructure. This tutorial by kasvith.me walks through building one from scratch using reverse proxying, round robin, and health checks.

How Has This Been Tested?

Verified the URL is accessible and the tutorial content is complete and well-structured.

Types of changes

• Content Update (change which fixes an issue or updates an already existing submission)
• New Article (change which adds functionality)
• Documentation change

Checklist:

• My code follows the code style of this project.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have made checks to ensure URLs and other resources are valid