Restructure frontend code to allow for extensions (#4721)

# Description of Changes
Move frontend code into `core` folder and add infrastructure for
`proprietary` folder to include premium, non-OSS features

frontend/src/core/tools/SwaggerUI.tsx

@@ -0,0 +1,24 @@
+import React, { useEffect } from "react";
+import { BaseToolProps } from "@app/types/tool";
+import { withBasePath } from "@app/constants/app";
+
+const SwaggerUI: React.FC<BaseToolProps> = () => {
+  useEffect(() => {
+    // Redirect to Swagger UI
+    window.open(withBasePath("/swagger-ui/5.21.0/index.html"), "_blank");
+  }, []);
+
+  return (
+    <div style={{ textAlign: "center", padding: "2rem" }}>
+      <p>Opening Swagger UI in a new tab...</p>
+      <p>
+        If it didn't open automatically,{" "}
+        <a href={withBasePath("/swagger-ui/5.21.0/index.html")} target="_blank" rel="noopener noreferrer">
+          click here
+        </a>
+      </p>
+    </div>
+  );
+};
+
+export default SwaggerUI;