This works, provided that:
- the package is on the catalog at pkgs.racket-lang.org
- the package is hosted on GitHub or GitLab
Restriction 2 could be lifted for other known sites or packages
hosted as directories.
Restriction 1 would be harder to lift.
This only links to the _top level_ file that defines the overall
document, not the file defining the particular section. Fixing that
would require the Scribble renderer to provide more detailed
information, although it's certainly a possible extension.
Closes#223Closes#208Closesracket/racket#874
Related to #76, #228
