How do I get Intellisense for JavaScript in VS Code to work? (npm installed @types)

I am writing a little web project with p5.js.

Basically it is just this right now:

<!DOCTYPE html>
<html lang="en">
<head>
  <script src="https://cdn.jsdelivr.net/npm/p5@1.4.1/lib/p5.js"></script>
  <script src="sketch.js"></script>
</head>
<body>
  <main>
  </main>  
</body>
</html>

I went ahead and installed the type definitions for p5.js like so:

npm install --save @types/p5

I was under the impression VS Code should pick up the type definitions for intellisense and use them when editing "sketch.js".

I tried to add a jsconfig.json to the root folder, but still no luck.