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/components/ui/label.tsx

@@ -0,0 +1,26 @@
+"use client"
+
+import * as React from "react"
+import * as LabelPrimitive from "@radix-ui/react-label"
+import { cva, type VariantProps } from "class-variance-authority"
+
+import { cn } from "@/lib/utils"
+
+const labelVariants = cva(
+  "text-sm font-medium leading-none peer-disabled:cursor-not-allowed peer-disabled:opacity-70"
+)
+
+const Label = React.forwardRef<
+  React.ElementRef<typeof LabelPrimitive.Root>,
+  React.ComponentPropsWithoutRef<typeof LabelPrimitive.Root> &
+    VariantProps<typeof labelVariants>
+>(({ className, ...props }, ref) => (
+  <LabelPrimitive.Root
+    ref={ref}
+    className={cn(labelVariants(), className)}
+    {...props}
+  />
+))
+Label.displayName = LabelPrimitive.Root.displayName
+
+export { Label }