Adds Global MLMU (#426)
* add global mmlu + zulu
* add global mmlu + zulu
* fix translatin literals
* add unk for global mmlu
* Update src/lighteval/tasks/multilingual/tasks.py
Co-authored-by: Clémentine Fourrier <22726840+clefourrier@users.noreply.github.com>
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Co-authored-by: Clémentine Fourrier <22726840+clefourrier@users.noreply.github.com>
