Type-safe LLM prompting.

`npm install promptgun`

Supports
- type-safe access and in-place docs for all openai models
- all prompts that request data output type-safe
- makes even streams type-safe
- subscribe to json elements as soon as they stream in
- extremely short, self-explanatory, discoverable, fluent syntax
- text prompts
- image prompts
- auto-retrying