[Feature Request] Chat interface to progressively build on queries

[alex-sun-kuo]

We envision users progressively building on their queries, instead of asking 1 time questions.

For example:

1. User asks "What are the 5 wealthiest cities in CA?"
2. CensusGPT responds with a SQL query, table, visualizer.
3. User asks "Which of these have the highest percentage of people with advanced degrees?"
4. CensusGPT refines original query, building on top of it to get the city with the highest population % with masters, professional school, doctorate degrees.

[alex-sun-kuo]

finished basic version of backend on dev: 81ff706

[asaprahul]

let's go!