Add AUTO_MODEL config

[piercegov]

When enabled, GPT will decide if it or DALLE should respond to the request. #67

Manually tested, works relatively well in practice. This does use two requests per input. Future iteration(s) could get around this by requesting GPT to answer inline if it finds that it is the best option to respond rather than DALLE.

For example, the prompt could be modified to be Given the following prompt, should ChatGPT handle this request, or should DALLE, an AI model that generates image? Respond with one word, either ChatGPT or DALLE. If ChatGPT is the best, then write "ChatGPT: " and then the response: ${prompt}

or similar.

[piercegov]

Actually maybe this feature should be disabled by default since it is more expensive to use.

[navopw]

Hey @piercegov, can you adjust the small things and I will merge it? 😄

Would be really nice.