Option to fill in own OpenAI key

[nelsonjchen]

It would be nice to have an option to replace the built-in key with our own OpenAI key. This is obviously not free for the user but it would be an optional hedge against OpenAI making it possible to see queries against a key such as one run by an external party and for those not wanting that code accessible to bloop's key.

e.g. https://news.ycombinator.com/item?id=35237458