Allow Dotenv implementation in load.environment.php to be backwards compatible.

[jonpugh]

I am running an automated upgrade as a test site for some Ansible I am developing using this repo.

Upgrading a site in place hits a snag when the autoloader includes load.environment.php (when upgrading from Drupal 8 to 9 only).

You can see in these logs that the method isn't found: https://github.com/opendevshop/devshop.platform/runs/3693762573?check_suite_focus=true#step:9:3504

PHP Fatal error: Uncaught Error: Call to undefined method Dotenv\Dotenv::createUnsafeImmutable() in /var/platform/apps/composerupgrade/d8localcomputer/load.environment.php:16

I'm not quite sure if this should be merged into the main project or not, but at the very least, this branch will exist for testing purposes.

Feedback welcome.

[AlexSkrypnyk]

This pull request/issue has been inactive for over a year and is being closed due to inactivity. If the issue still persists or the contribution is still relevant, please feel free to reopen it or create a new one.

Thank you for your understanding and your contributions to the project!