Adding Level Based Foraging to BenchMARL.

Hello,

Firstly, BenchMARL has been very helpful for me. I sincerely thank everyone involved for their efforts.

Can we look to add Level Based Foraging ([LBF](https://github.com/semitable/lb-foraging)) to BenchMARL? I have been using LBF for a while, and it is very well supported by [epymarl.](https://github.com/uoe-agents/epymarl) Benchmarking has also been done on LBF in this [paper.](https://arxiv.org/pdf/2006.07869)

Please let me know if this could be helpful.

Start by reviewing BenchMARL's existing task integrations and the linked Level Based Foraging project, then compare how epymarl supports LBF. Determine the integration points needed to make LBF available for BenchMARL benchmarking; done means the environment can be selected and benchmarked consistently within BenchMARL.

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