`man info` inadequate for `info info`

[Will Mengarini]

Standalone info is documented by `info info`, using which requires
knowledge of its keybindings, which are not documented in `man info`.

They're documented in `info info`, but that's inaccessible without
some clues (cursor movement, next/previous/up node, quit) that should
be documented in the man page to allow a new info user to get started.