This is spreadsheet imlemented as a web component. If you examine the index.html file, you'll see that to use it all you have to do is import the javascript and then put a tag on the page: <wc-spread-sheet></wc-spread-sheet>.
Web components allow encapsulation, protecting data and styles from leaking out into the rest of the page.
And from developer.mozilla.org:
Web Components is a suite of different technologies allowing you to create reusable custom elements — with their functionality encapsulated away from the rest of your code — and utilize them in your web apps.
By their very nature, web components are composable. And they offer true encapsulation through the shadow DOM. You can make component properties observable so that when their values change, the component updates automatically. Since the browser is responsible for the update, this will happen far faster than any JavaScript library can do.
Because web components are based on standards supports by all currently shipping browsers, you can be sure any web components you create will work as expect indefinitely. You do not have to worry about features being deprecated and labeled "unsafe" or "dangerous" like libraries often do. In fact, because web components are part of the browser, you can use them with any other frontend library.
This project illustrates another advantage of web components: no need to build. Everything runs live in the browser. This is accomplished through ES modules.
To ease the definition of web components, I've used Lit-Element from the Polymer Project. Lit-Element is a tiny library that provides convenience methods to simplify the definition of custom elements.
If you're new to web components and would like to know how to get started creating and using them, a good place to go is Open-WC. They provide a number of useful guides for setup, development, testing and publishing.