GitHub action vs using podman locally

https://github.com/federlieb/federlieb/actions/runs/4590469738 - I am trying to use podman on my development machine and have to use docker via GitHub actions. https://code.visualstudio.com/remote/advancedcontainers/docker-options suggests to use `"runArgs": [ "--userns=keep-id" ],` but it seems docker does not support that, hence the failure of my action.

I have tried setting the podman option with the `PODMAN_USERNS` environment variable, which the command line option defaults to, according to their documentation, through `devcontainer.json` `remoteEnv`, but that does not have the same effect as the command line argument, at least not locally.

I naturally want my devcontainer as well as the CI action to work regardless of whether any given host uses docker or podman. What is the proper way to configure my project accordingly?