Add a fact checker feature with updated styling (#835)

- Add an experimental feature used for fact-checking falsifiable statements with customizable models. See attached screenshot for example. Once you input a statement that needs to be fact-checked, Khoj goes on a research spree to verify or refute it.
- Integrate frontend libraries for [Tailwind](https://tailwindcss.com/) and [ShadCN](https://ui.shadcn.com/) for easier UI development. Update corresponding styling for some existing UI components. 
- Add component for model selection 
- Add backend support for sharing arbitrary packets of data that will be consumed by specific front-end views in shareable scenarios

src/interface/web/app/components/referencePanel/referencePanel.module.css

@@ -2,7 +2,6 @@ div.panel {
     padding: 1rem;
     border-radius: 1rem;
     background-color: var(--calm-blue);
-    color: var(--main-text-color);
     max-height: 80vh;
     overflow-y: auto;
     max-width: auto;