add a menu item to add (the appropriate) racket/bin
to the users' path under mac os x

it is in the help menu, but I'm not sure that's really
the best place
Rackety
minor edits & mention plural
use find-console-bin-dir instead of find-system-path to find the bin dir
missed some edits in my last attempt ...
fix path in source-distribution README

Closes PR 14065
make installers: support Mac OS X ".pkg" format

The ".pkg"-based installer doesn't provide the option of picking
an installation path, but it can add a path in "/etc/paths.d"
so that users do not have to explicitly set the `PATH` environment
variable.
make site: add support for help pop-ups on generated download page
fix `runtime-require` duplicate path registration
fix "base" and "compatibility" test drivers
Correct unary minus in complex numbers.
Make float complex multiplication not optimize on number expressions.
Minor fix to number matching in complex opts.
Make conjugate correctly optimize.
Make float-complex optimizations be more picky.
Move unboxed tables to seperate file.
Move uses of unboxed-vars to centralized definition.
Make function for adding vars to unboxed vars table.
Make function for adding an unboxed function.
Add syntax class for unboxed functions.