Update index.md: link IteratedIntegration.jl

Author: stevengj

docs/src/index.md

@@ -77,7 +77,7 @@ part of your domain (e.g if your integrand has a sharp peak or singularity
 somewhere that is not known in advance).
 
 For multidimensional integration, see also the [HCubature.jl](https://github.com/stevengj/HCubature.jl), [Cubature.jl](https://github.com/stevengj/Cubature.jl), and
-[Cuba.jl](https://github.com/giordano/Cuba.jl) packages.
+[Cuba.jl](https://github.com/giordano/Cuba.jl) packages, or alternatively [IteratedIntegration.jl](https://github.com/lxvm/IteratedIntegration.jl) for efficient nested 1d integrals (probably more efficient than nesting QuadGK directly).
 
 Note that all of the above quadrature routines assume that you supply you integrand
 as a *function* $f(x)$ that can be evaluated at *arbitrary points* inside the