Byron/dua-cli

AI Summary: Add a new command-line option to the `dua` CLI tool to output disk usage data in a format compatible with flamegraph.pl (or similar tools). The output should be a single line per file/directory, with path separators replaced by semicolons, and special characters replaced by underscores. Hard link handling is optional but preferred. This involves modifying the existing code to generate the specific output format and potentially adding logic to handle hard links efficiently.