Feature/skip existing

[pyousefi]

Description

New parameter: -s, --skip; will ⏭️ Skip existing files and directories that are provided in the tree structure. Motivation is captured in feature request.

Fixes # 17

Type of change

Please delete options that are not relevant.

• 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 not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement

How Has This Been Tested?

New test added: test('should skip existing files and directories when skip option is enabled'

• [X ] Test A (e.g., npm test)
• Test B (e.g., Manual testing with X input)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Additional Notes

Add any other context about the pull request here.