Unfortunately, this hasn't been updated for v2 of uibuilder, it refers to v1. Sorry, that should be clearer on the page.
You will need to translate the links in your index.html code from the v1 format to the v2 format.
<link rel="stylesheet" href="vendor/normalize.css/normalize.css">
<link rel="stylesheet" href="index.css">
<!-- include riot.js and the compiler -->
<!-- NB: Normalize no longer included by default, use uib's library manager to install it if you want it --->
<link type="text/css" rel="stylesheet" href="../uibuilder/vendor/normalize.css/normalize.css" />
<link type="text/css" rel="stylesheet" href="./index.css" media="all">
<!-- Not sure you really want this - will have to be installed via uib library manager --->
<!-- <script src="./uibuilderfe.js"></script> //dev version -->
<script src="./uibuilderfe.min.js"></script> <!-- //prod version -->
../uibuilder/vendor/ which are different. The first gives you resources from your own front-end code, the second gives you access to uibuilder's shared resources.
The other difference from when Kazushige wrote that WIKI article is that normalize.css and jquery are no longer included by default (you may not need them anyway). Also, you can now install front-end libraries like Riot using uibuilder's own library manager from the Node-RED editor.
Finally, you should note that the article uses RiotJS v3 which is no longer current - I'm afraid that I don't know what changes you would need for v4.
When you get this working, it would be great to get that article updated (or a new one added) if you fancy that so that others can benefit?