If platform bindings go into `extras/` then extras aren't really "built upon" the main component(s)

[david-bakin]

w.r.t. the first paragraph of 4.4 extras/:

I get why platform bindings are not in libs/ as they're not always built and that's a requirement for the submodules in libs/. (Some people may never build the Windows bindings, others never build the Linux bindings ...) But typically one or another of them is always required for any given build. They're at the foundation of the project.

So I'm fine with them in extras but the wording of what goes in extras should be changed ...

Or maybe it's the requirement that stuff in libs/ is always built that should be relaxed ...

But actually, in my own project, I'm putting them as submodules in libs/.

(In fact, I have added another layer inside of libs/ where I group submodules by "category" - I may have multiple implementations of a given service interface, for example, so I put them together under, say, "storage" (one submodule for sqlite, one for filesystem, one for webdav, ...) - and in this way I'll have libs/platform/ and there will be under it windows and linux (macos can go into extras/ with any other contributed stuff...).)

(Pitchfork is well thought-out IMO, thanks for the effort!)