How to use plugins inside a docker container

[gourvy]

Hello!

I succeeded to use some plugins inside a docker container. For long hours I came across this error:
[ ERROR ] The specified engine has not resolved.
This is an example of successful build:
engine.js:

const markdownItMark = require('markdown-it-mark')
module.exports = ({ marp }) => marp.use(markdownItMark)

Dockerfile:

FROM marpteam/marp-cli:latest                                                                                                                                                                 

RUN npm install -g --save-prod markdown-it-mark

ENV NODE_PATH=/usr/local/lib/node_modules

Command line:
docker build -t my_marp
docker run --rm --init -v $PWD:/home/marp/app/ -e LANG=$LANG -e MARP_USER="$(id -u):$(id -g)" my_marp slide-deck.md --engine ./engine.js

I think that there's probably some room for improvement (npm install -g --save-prodis probably not the best line) but this could be part of the documentation.