It's a library AND a binary, but at what cost?

This is a simple toy project that demonstrates the various failure modes of trying to make a single cargo package a libary and a binary.

• v0.1.0 is a package that can't be published because its binary's dependences are behind a feature="cli"
• v0.2.0 is a package that has bin.required-features = ["cli"], resulting in cargo install failing to install
• v0.3.0 is a package that enables the cli by default with features.default = ["cli"], resulting in cargo add adding too much to library users