Add link to ldlasb2 and its benchmarks writeup

Author: eddelbuettel

ChangeLog

@@ -1,3 +1,7 @@
+2025-09-11  Dirk Eddelbuettel  <edd@debian.org>
+
+	* README.md: Link to ldlasb2 repo and its 'benchmarks' writeup
+
 2025-09-10  Dirk Eddelbuettel  <edd@debian.org>
 
 	* inst/skeleton/Makevars (PKG_CXXFLAGS): Remove outdated comments

README.md

@@ -76,6 +76,9 @@ C++17](https://cran.r-project.org/doc/manuals/r-devel/R-exts.html#Portable-C-and
 since version 4.3.0. See [GitHub issue #475](https://github.com/RcppCore/RcppArmadillo/issues/475)
 for more about choosing between 'legacy' Armadillo 14.6.3 or 'current' Armadillo 15.0.1 or later.
 
+Performance is excellent, and on par or exceeding another package claiming otherwise. See [this
+post][benchmark] and its [repo][ldlasb2] for a detailed debunking of that claim.
+
 ### Documentation
 
 The package contains a pdf vignette which is a pre-print of the
@@ -110,3 +113,5 @@ GPL (>= 2)
 [rcpp]: https://www.rcpp.org
 [cran]: https://cran.r-project.org
 [cran pkg]: https://cran.r-project.org/package=RcppArmadillo
+[benchmark]: https://eddelbuettel.github.io/ldlasb2/benchmarks.html
+[ldlasb2]: https://github.com/eddelbuettel/ldlasb2