Support for binary targets

[mattmassicotte]

Feature Request: Support for binary targets

Description:

I make an xcframework, distributed as a SPM binary target. As far as I can tell, there is no way for me to incorporate DocC support for it directly in the package. I think it would be really nice to be able to incorporate documentation.

Motivation:

It is totally possible to get this to work out-of-band. But, especially with things like the Swift Package Index building and hosting documentation, finding a way to officially support it would be much more convenient. And, could also help encourage better documentation for binaries distributed this way.

Importance:

While my particular package is also open source, I think may binaries distributed this way are not. Encouraging better documentation for these cases would be really welcome.

Alternatives Considered

It is possible to get this to work with a custom solution, outside of SPM. But, its a pain, and doesn't work with existing tooling, particularly SPI.