fix(default): only use `woman` on macOS
fix(default): only use `woman` on macOS

`man -k "^"` is very slow on macOS.

```
sh-3.2$ time man -k "^" > /dev/null

real	0m1.599s
user	0m0.391s
sys	0m1.209s
```

hlissner/doom-emacs,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/doom-emacs,hlissner/doom-emacs,hlissner/doom-emacs,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/doom-emacs,hlissner/doom-emacs,hlissner/doom-emacs,hlissner/.emacs.d,hlissner/.emacs.d,hlissner/.emacs.d