`custom-elements/extends-correct-class` should check if the parent class extends `HTMLElement`

Currently, `custom-elements/extends-correct-class` checks if the custom element extends HTMLElement. However, it triggers an error if the class I want to extend extends `HTMLElement`.

Example:

```javascript
class A extends HTMLElement {}

class B extends A {}

if (!window.customElements.get('custom-el')) {
  window.customElements.define('custom-el', B);
}
```