feat: Add multilabel classification for training (#191)

* Added multilabel option to training

* Added multilabel option to training

* Added multilabel option to training

* Added multilabel option to training

* Added multilabel option to training

* Added multilabel option to training

* Added threshold to predict

* Updated docs

* Updated docs

* Removed fallback logic

* Updated docs

* Updated docs

* Resolved feedback

* Update model2vec/train/README.md

Co-authored-by: Stephan Tulkens <stephantul@gmail.com>

* Resolved feedback

* Resolved feedback

* Resolved feedback

* Resolved feedback

* add multilabel targets, fix tests (#194)

* Fixed bug with array conversion

* Optimized inference performance

* Changed classes to np array

* Added int as possible label type

* Added int as possible label type

* Use previous logic

* Updated type check

* Updated type check

* Updated type check logic

* Only return object type array for multilabel

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Co-authored-by: Stephan Tulkens <stephantul@gmail.com>