Add docs for neovim-remote integration for fish

[aabccd021]

Fish has different syntax for setting up neovim-remote:

if [ -n "$NVIM_LISTEN_ADDRESS" ];
    alias nvim="nvr -cc split --remote-wait +'set bufhidden=wipe'"
end

if [ -n "$NVIM_LISTEN_ADDRESS" ];
    set -x VISUAL "nvr -cc split --remote-wait +'set bufhidden=wipe'"
    set -x EDITOR "nvr -cc split --remote-wait +'set bufhidden=wipe'"
else
    set -x VISUAL "nvim"
    set -x EDITOR "nvim"
end

Can we add this to readme?

[nicoandresr]

also mention it should be put inside ~/.config/fish/config.fish