zsh: improve tab completion of `j` function/alias
zsh: improve tab completion of `j` function/alias

Completes hashed directories and directories. Handles both once
completed.

wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent