Add verbose flag for debugging

## Proposal

Need add `verbose` flag for getting details information about build

## Use case

```sh
themekit build --verbose
```

Start by locating the CLI entry point for `themekit build` and its existing option parsing. The issue does not identify which build details verbose mode should show, so clarify the expected output before implementing and verify the command with `themekit build --verbose`.

Written by the indexing model from the issue text.