docs: added UI link to navigation bar (#4796)

www/api-reference/components/Navbar/index.tsx

@@ -40,6 +40,7 @@ const Navbar = () => {
               label="Admin API"
               activeValue="admin"
             />
+            <NavbarLink href="https://docs.medusajs.com/ui" label="UI" />
           </div>
         </div>
         <div className="hidden min-w-0 flex-1 items-center justify-end gap-0.5 lg:flex">

www/docs/docusaurus.config.js

@@ -101,6 +101,13 @@ const config = {
           target: "_blank",
           position: "left",
         },
+        {
+          href: `${process.env.API_URL}/ui`,
+          label: "UI",
+          prependBaseUrlToHref: true,
+          target: "_blank",
+          position: "left",
+        },
         {
           type: "search",
           position: "right",