Add usage of hapi/topo to sort through the plugin list.

[osukaa]

I was recently creating new apps and needed to sort through the plugin list. It is sometimes unavoidable. I think hapipal folks explained it better here: https://github.com/hapipal/hapipal.com/blob/master/lib/content/best-practices/handling-plugin-dependencies.md

I was inspired by (the now archived) steerage.

This change should be backward compatible.