Integration of new models: Top2Vec and BERTopic

[pasqLisena]

• Top2Vec: https://arxiv.org/abs/2008.09470 with github at https://github.com/ddangelov/Top2Vec and REST API https://github.com/ddangelov/RESTful-Top2Vec

• BERTopic: https://github.com/MaartenGr/BERTopic