docs(readme): update regarding hardlinks

Author: KSXGitHub

README.md

@@ -50,13 +50,14 @@ The benchmark was generated by [a GitHub Workflow](https://github.com/KSXGitHub/
 * Very fast.
 * Relative comparison of separate files.
 * Extensible via the library crate or JSON interface.
+* Unbiased regarding hardlinks: All hardlinks are treated as real files.
+* Optional hardlink detection and deduplication (would make `pdu` proportionally slower).
 * Optional progress report (would make `pdu` slightly slower).
 * Customize tree depth.
 * Customize chart size.
 
 ## Limitations
 
-* Ignorant of hard links: All hard links are counted as real files.
 * Do not follow symbolic links.
 * Do not differentiate filesystem: Mounted folders are counted as normal folders.
 * The runtime is optimized at the expense of binary size.