Problem
I have not installed Caddy on my dev machine and do not wish to do so. However, I still want to use caddy fmt.
It's easy to run it manually via Docker but doesn't leverage the full features of this extension.

Solution
I wrote a super simple wrapper script to make this extension work with a dockerized Caddy. It could be interesting to add it to the documentation. It works on MacOS (and most likely on Linux, not tested).

#!/usr/bin/env bash

cat /dev/stdin | docker run --rm -i --entrypoint caddy caddy:2.6-alpine "$@"

Once the script is set up somewhere, just point caddy.executable to it and it works.