Add a fact checker feature with updated styling

[sabaimran]

• 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 and ShadCN 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