Structure for a hybrid package with two modules and binaries
Both @c-blake and I tried to find a way to convince Nimble to install a package that has two `.nim` files where both files are supposed to be both Nim modules and binaries. In other words, both modules contain a `when isMainModule` statement.

The package in question is https://github.com/c-blake/hldiff . I had opened a [ticket](https://github.com/c-blake/hldiff/issues/1) there which contains a discussion of our so far unsuccessful attempts.

On the Nimble side, I don't know if https://github.com/nim-lang/nimble/issues/747 is somehow related. That ticket describes a different problem though.

What I'd like is a suggestion for a working package setup for `hldiff` and if possible an explanation for this setup, so we can transfer this knowledge to future packages. Once we have found a suitable setup, it'll probably make sense to update the Nimble readme to contain the necessary background information to arrive at this setup.