feat: using env variables on simulation file

[fgalan]

PR looks good, but documentation and changelog aspects should be taken into account. In particular:

Regarding documentation, I'd suggest to extend the scope of the current simulation-configuration-file.md, so:

• simulation-configuration-file.md to be renamed to simulation-configuration.md
• Change in mkdocs.yml file to:

- 'Simulation configuration': 'simulation-configuration.md'

• Add a new section in simulation-configuration.md file about "Simulation configuration using environment variables" which explains the new funcionality.

Regarding changelog, I'd sugges the following entry:

- Add: environment variables based configuration using .env files

or something like that.