[plans] Add a symlink `vi` in `core/vim`.
[plans] Add a symlink `vi` in `core/vim`.

This will add `vi` onto a Plan author's `$PATH` if they are in an
interactive Studio.

Signed-off-by: Fletcher Nichol <fnichol@nichol.ca>

Pull request: #743
Approved by: fnichol

rsertelon/habitat,habitat-sh/habitat,rsertelon/habitat,rsertelon/habitat,habitat-sh/habitat,habitat-sh/habitat,georgemarshall/habitat,nathenharvey/habitat,nathenharvey/habitat,georgemarshall/habitat,habitat-sh/habitat,rsertelon/habitat,habitat-sh/habitat,habitat-sh/habitat,georgemarshall/habitat,georgemarshall/habitat,georgemarshall/habitat,georgemarshall/habitat,nathenharvey/habitat,rsertelon/habitat,georgemarshall/habitat,habitat-sh/habitat,rsertelon/habitat,nathenharvey/habitat,nathenharvey/habitat,georgemarshall/habitat,rsertelon/habitat,nathenharvey/habitat,habitat-sh/habitat