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/navMenu/navMenu.module.css

@@ -1,5 +1,4 @@
 menu.menu a {
-    color: var(--main-text-color);
     text-decoration: none;
     font-size: medium;
     font-weight: normal;
@@ -51,7 +50,6 @@ div.settingsMenuProfile img {
 }
 
 div.settingsMenu {
-    color: var(--main-text-color);
     padding: 0 4px;
     border-radius: 4px;
     display: flex;