Custom environment

[Janez88]

Adding custom environment by following the README.md in examples/extending/task instructions doesn't work. Doing it by this method results in circular import of Task class. As this is an essential and vital part of BenchMARL, I kindly seek help in the process and suggest improvements to README.md for clarifying the intended use and provide greater assistance.

[Xmaster6y]

Maybe you can provide more info about your setup/error, because the explanations look legit.