add bill summaries generated from GPT based on legislative text

[derekeder]

to help search and user comprehension, lets have ChatGPT summarize bills for us to display. We'll want to limit the number of bills we do this on, likely just on non-routine.

We're going to refine our topics classification in #408 first to help narrow this set of bills down first

[derekeder]

we have this in place now in the extras field of billversion as summary. I'll work on displaying on the front end

[derekeder]

if we want to improve the quality of the legislative summary, @antidipyramid mentioned it might be helpful to use https://github.com/explosion/spaCy