feature: tree stack implementation

[lcweden]

This pull request introduces the initial implementation of the tree-stack package, providing a lightweight, configurable utility for rendering hierarchical tree-view prefixes. It includes the core TreeStack class, comprehensive documentation, automated tests, and CI/CD workflows for versioning and publishing. The most important changes are:

Core Implementation:

• Added the main TreeStack class in mod.ts, supporting configurable branch characters and methods for managing tree hierarchy state (enter, leave, next), along with TypeScript types and JSDoc documentation.

Documentation:

• Added a detailed README.md with installation instructions, usage examples, API documentation, and customization options.
• Added an MIT LICENSE file.

Testing:

• Added a comprehensive test suite in mod.test.ts covering all core behaviors, edge cases, and formatting scenarios.

Tooling & Automation:

• Added deno.json with package metadata, build/lint/test scripts, and import maps.
• Added GitHub Actions workflows for CI (ci.yml), version bumping (bump.yml), and publishing to npm/JSR (publish.yml). [1] [2] [3]

Development Environment:

• Added .devcontainer and .vscode configuration files to support Deno development in VS Code with recommended extensions. [1] [2] [3]
  [Copilot is generating a summary...]