add model for auto-complete (FITM, fill in the middle)

This would plug beautifully into Continue and others that leverage FITM models with custom endpoints like Venice.ai API

“An "autocomplete model" is an LLM that is trained on a special format called fill-in-the-middle (FIM). This format is designed to be given the prefix and suffix of a code file and predict what goes between. This task is very specific, which on one hand means that the models can be smaller (even a 3B parameter model can perform well). On the other hand, this means that Chat models, though larger, will perform poorly.”
https://docs.continue.dev/customize/model-types/autocomplete