Subcommand to create a new WordPress site

It would be nice to have a subcommand that walked you through the process of setting up an new WordPress site.

These pieces would include:
- [ ] Download WordPress to a directory if it doesn't exist in the directory.
- [ ] Create a database if one doesn't exist.
- [ ] Create a `wp-config.php` file if one doesn't exist.
- [ ] Install WordPress (either single site or multisite).

This will make a multi-step process into a single-step process.

Start by reviewing the repository's existing command structure and the WordPress setup flow. Define how the subcommand should handle downloading WordPress, creating the database and wp-config.php, and installing single-site or multisite; done means the full setup works as one guided command.

Written by the indexing model from the issue text.