Allow instructor to ignore certain fields

[srcrip]

This is my take at solving: https://github.com/thmsmlr/instructor_ex/issues/92

I came to the linked issue because I wanted to use the Gemini adapter with a schema I had that used regular map types. Unfortunately, you can't do that with Gemini.

In my case the field that was a map I didn't even care about returning from the llm, so I wanted a way to just make instructor ignore it--then I saw that there was an open issue requesting the same thing so I just went for it.

[srcrip]

Still need to workshop this a bit because its not quite working yet