I'm currently working on an implementation of "educational notes" for diagnostics as described here. I haven't settled on a set of style guidelines yet, but these will probably be 1-2 paragraphs each, so I'm not sure it's a good idea to define them with macros/tablegen and include them in the binary.
Instead, I've been thinking about shipping them in the toolchain as documentation resources that can be loaded as needed.
usr/share/doc seems like a good candidate for this sort of thing, but I'm interested in hearing other's opinions. Down the road this might be a good way to ship a local copy of the stdlib docs as well if we ever decide to do that.