Adds context as first-class feature of Model.

[mbleigh]

This adds the ability to pass context (an array of DocumentData[]) to a model and adds default support for prompt augmentation if a model does not declare specific support for context. Usage:

const query = "What do cats like to eat?";
const docs = await retrieveStuff({query});

generate({
  prompt: `Answer this question: ${query}`,
  context: docs
});

This will augment the prompt to look something like this:

Answer this question: What do cats like to eat?

Use the following information to complete your task:

- [0]: Cats eat a variety of foods including dry kibble and wet foods that can be purchased at a pet store.
- [1]: Cats will hunt mice and birds for fun and for food.

[maxl0rd]

I think this looks good. I like how dotprompt will let you position the context in the template.

Made one comment where I think you could thread it through to vanilla prompts too.