Document Copilot BYOK (bring your own key)

[isidorn]

We should document our Bring Your Own Key offering.

@ntrogh any thoughts where these docs should live?

[ntrogh]

@isidorn Thought about adding an "AI Models" article in the Copilot docs. That would cover both changing the model for chat, completions, and BYOK.

[isidorn]

This makes sense to me. Not sure if "AI Models" is the right name. I see you already use it, so it might work.
Alternative is "Language Models" or "AI Language Models"

[ntrogh]

Will go with "AI Language Models"