Reference to a package main page

[Julow]

It's not possible to reference a package main page, which is not a special concept in Odoc but currently a regular page (#1037).

Drivers currently change the name of the index.mld page and there's no conventional name (Dune names it <package name>.odoc but Voodoo names it <version string>.odoc).

This might also be used to write unambiguous fully-qualified references in the future (eg. package_name.library.Module).

[jonludlam]

This is possible now as {!//page-index} (or {!/foo/page-index} for a different package)

[dbuenzli]

This is possible now as {!//page-index}

Would be worth adding it to the docs