Support for a limited vocabulary for generation

**Is your feature request related to a problem? Please describe.**
I would like to constrain the model output to only use a custom vocabulary comprising a list of allowable words (or alternatively, to blacklist all other words in the vocabulary).

**Describe the solution you'd like**
HuggingFace's transformer library features a `bad_words_id` keyword in the `model.generate` function that accepts a list of words to exclude from its output (some discussion of this feature [here](https://github.com/huggingface/transformers/issues/21961)).

**Describe alternatives you've considered**
Could this possibly be achieved with the use of a `llama_cpp.LogitsProcessor`? I am less familiar with this library and haven't found examples in a similar direction, so am unsure how straightforward this could be to implement using one of those.