docs: Add JSDoc documentation for register() function

[MzyzzG]

Summary

Adds comprehensive JSDoc documentation to the register() function in registry.js.

Changes Made

• Added JSDoc comment block above exports.register
• Documents @param, @example, and @throws
• Explains module types and registration process

Benefit to Maintainers

• Helps new contributors understand how to register modules
• Provides code examples for common use cases
• Follows existing documentation patterns in the codebase
• Zero functional impact, documentation only

Type of Change

• Bug fix
• New feature
• Documentation update
• Refactor

[emilykl]

Hi @MzyzzG, the file already contains a detailed docstring for the register() function, so I'm going to close this PR.