Reduce npm Package Size by Excluding `templates/` Directory from Distribution

The `templates/` directory in our npm package contains various templates used for scaffolding code. As we continue to add more templates, the size of the npm package will increase unnecessarily, leading to version inflation and potential issues for users with limited bandwidth.

## Proposed Solution:

Exclude the `templates/` directory from the npm package by adding it to `.npmignore`.
Modify the `bin/universal-box.js` script to dynamically display available template options by iterating through the `templates/` directory.
Since the `templates/` directory will not be present in the npm package, we can create empty directories representing each template just to display the options. These empty directories won't be ignored by `.npmignore`.
When a user selects a template, the corresponding directory should be cloned from the repository, pulling in the necessary files only when needed.

## Expected Outcome:

Reduced package size, making it more efficient to install and update.
Users will still be able to see all available templates and select them for scaffolding without downloading unnecessary files.

Open to further discussions

Examine the .npmignore file and the bin/universal-box.js script. Understand how templates are currently included and used. The change involves updating .npmignore to exclude the templates/ directory, then modifying the CLI script to list templates by reading the repository (likely via Git) instead of the local directory, and cloning the selected template on demand. Test the package build and installation locally to ensure the CLI still works without the templates directory present.

索引モデルが issue の本文から書いたものです。