feat: Initial DSL setup

[LMLiam]

Summary

Introduce the foundational Kotlin DSL for Adventure component building

Why is this needed?

This provides a structured, ergonomic entry point for contributors and downstream plugin authors to define Adventure components declaratively.

Proposed solution

• Create base builder interfaces and extension functions.
• Document the builder syntax in README with annotated examples.

Checklist

• I have searched existing issues to avoid duplicates