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

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",