Multi-line environment files are not correctly processed

[hedayat]

Describe the bug
For environment files, podman-compose passes them to podman with its --env-file option. However, podman/docker and docker-compose process environment files differently: podman/docker doesn't support multi-line environment files, while docker compose supports them (containers/podman#18724 (comment)).

Expected behavior
Properly support multi-line env files

Actual behavior
Just passes env-files to podman, which doesn't support multi-line env vars, as apparently docker also doesn't support them too.

** Implementation **
I found that it can be easily implemented (parse env file with dotenv, and pass variables to podman), and I'll open a PR to fix it too.