The back-end is largely package type agnostic and the package manager front-ends are pluggable. I'd look for AWS to expand package manager support in the near future. Nuget was on the list along with a few other popular package managers. There's a whole lot of functionality in the platform they didn't yet expose or have finished for the launch, I'd keep an eye on this as they move forward.

Source: I lead the technical design for the product as well as a chunk of the implementation but left the team mid-2018. I don't have any specific insight into their plans, not that I could really share them even if I did.