Eleventy, LiquidJS, and redefining the Markdown library

Question

I have an Eleventy site where I've redefined the markdown library in order to enable footnotes.

let markdownIt = require("markdown-it");
let markdownItFootnote = require("markdown-it-footnote");
let options = {
  html: true,
  breaks: true,
  linkify: false
};

let markdownLib = markdownIt(options).use(markdownItFootnote);
config.setLibrary("md", markdownLib);

I'm also trying to implement responsive images via the eleventy-img plugin, however it seems by redefining Markdown-It I've lost LiquidJS preprocessing and can't use Liquid-based shortcodes in markdown content (and therefore can't use the async keyword required to get useful responsive images via the plugin's examples). Is there some way to configure Eleventy to get both?