User interface to build a custom bootstrapper for Cake

Cake offers a few examples of bootstrappers in the [resources repo](https://github.com/cake-build/resources/) which are meant to be a starting point for developers using Cake, and it's encouraged that they be customized to meet each project's needs.

One of the challenges of offering these bootstrapper templates is choosing which steps should be performed as a "default" starter template as discussed in https://github.com/cake-build/resources/issues/95, and one idea that could make this experience more interesting would be to put together a "bootstrapper builder" UI where users can cherry-pick things they want and download a more customized boostrapper based on their preferences. Something along those lines: