Its a Custom Web Component. Do not use the constructor directly with the new keyword. Instead, use one of the 3 following methods:

Create the Web Component and call its init method:

const myButton = document.createElement("a-button").init(config)

Or use the shorthand for it:

const myButton = createButton({
 text: "Click me!",
 icon: "fas fa-check",
 action: () => console.log("click!")
})

myButton.render()

Or directly declare the config inside a container component:

const myPanel = createPanel({
  title: "My panel",
  items: [
      {
          type: "button",
          text: "Click me!",
          icon: "fas fa-check",
          action: () => console.log("click!")
      }
  ]
})
myPanel.render()