Make it easier to set container environment variables

[lizardruss]

Is your feature request related to a problem? Currently, users must create and mount a config map or secret using the --from-env-file option in order to make variables from a .env available in a container environment.

Which solution do you suggest? Add a convenience option to devspace.yaml configuration that will create and mount a config map or secret created from a .env file.

Which alternative solutions exist? Manually manage creating and deleting a config map or secret using pipelines.

Additional context Inspired by a discussion in the Loft Users Slack.