Update README.md to accurately generate a yaml file at the instructed…

[heaversm]

… location

Without the output format specified in the yaml, a file is not generated (outputs in console). Also, extension not necessary (or honored, I think) in CLI

Types of changes

• [ ] Enhancement (project structure, spelling, grammar, formatting)
• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.

A description of the changes proposed in the Pull Request