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/factchecker/layout.tsx

@@ -0,0 +1,25 @@
+
+import type { Metadata } from "next";
+import NavMenu from '../components/navMenu/navMenu';
+import styles from './factCheckerLayout.module.css';
+
+export const metadata: Metadata = {
+    title: "Khoj AI - Fact Checker",
+    description: "Use the Fact Checker with Khoj AI for verifying statements. It can research the internet for you, either refuting or confirming the statement using fresh data.",
+    icons: {
+        icon: '/static/favicon.ico',
+    },
+};
+
+export default function RootLayout({
+    children,
+}: Readonly<{
+    children: React.ReactNode;
+}>) {
+    return (
+        <div className={styles.factCheckerLayout}>
+            <NavMenu selected="none" />
+            {children}
+        </div>
+    );
+}