[FIX] Implement Custom Directory Tree Method

[eli64s]

The README's directory tree is now generated using pure Python.

• Removes dependency on the tree command keeping it native to Python
• Improves security by removing the subprocess module.

In the original implementation, if the desired executable path is not fully qualified relative to the filesystem root then this may present a potential security risk.

def run_tree_command(repo_path: Path) -> str:
    """Executes the 'tree' command to generate a directory tree."""
    tree_bytes = subprocess.check_output(["tree", "-n", repo_path])

More details on this can be found here

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