[cmd] use hiccup-cli with neovim

[humorless]

Installation and configuration

1. Download the hiccup-cli binary from here.
2. Move hiccup-cli to /usr/local/bin/hiccup-cli
3. Because the hiccup-cli does not support reading from stdin, I need to configure it with a bash script html2hiccup.

#!/usr/bin/env bash

middle="$(mktemp)"
while IFS= read -r line; do
    echo "$line" >> "$middle"
done

hiccup-cli --html-file "$middle"

Move the script html2hiccup to /usr/local/bin/html2hiccup

Screenshots

vim reference with external command