docs/getting_started: clarify ~/.emacs.d/bin entry in PATH
docs/getting_started: clarify ~/.emacs.d/bin entry in PATH

I took this for granted:

Works:
  export PATH=~/.emacs.d/bin:$PATH
  export PATH="$HOME/.emacs.d/bin:$PATH"

Does not work:
  export PATH="~/.emacs.d/bin:$PATH"

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