Function ImageConverterPrompt

ImageConverterPrompt(filepath: string, filename: string): Promise<void>
Orchestrates the image conversion process, guiding the user through:
- selecting files,
- choosing output format,
- setting advanced options, and
- specifying output names.
Parameters
- filepath: string
  The path to the directory containing the images. If empty, defaults to the current working directory.
- filename: string
  The name of the file or directory within the filepath. If filepath is empty, this parameter is ignored.
Returns Promise<void>
- Resolves when the conversion process is complete.