Add doc page on computing Least Squares.
diff --git a/doc/snippets/LeastSquaresQR.cpp b/doc/snippets/LeastSquaresQR.cpp
new file mode 100644
index 0000000..6c97045
--- /dev/null
+++ b/doc/snippets/LeastSquaresQR.cpp
@@ -0,0 +1,4 @@
+MatrixXf A = MatrixXf::Random(3, 2);
+VectorXf b = VectorXf::Random(3);
+cout << "The solution using the QR decomposition is:\n"
+     << A.colPivHouseholderQr().solve(b) << endl;