The top-level version: "2" field is ignored by modern Docker Compose,
which warns about it on every invocation. Drop it from docker-compose.yml
and the compose-dev-backend, compose-dev-frontend and compose-e2e-test
files.
This commit replaces all references to `umputun/remark42` Docker images
on Docker Hub with `ghcr.io/umputun/remark42` from the GitHub
Container Registry. It updates various Docker Compose files,
documentation, and the Makefile to use the new image location.
It also updates the kubernetes example to use the latest version.
Docker Hub is going to kill free pulls for too long by now.
Dmitry VerkhoturovandUmputun
Pavel MineevandDmitry Verkhoturov