IntersectionObserverInit.root should accept type Document

[troyt-42]

According to https://w3c.github.io/IntersectionObserver/#dictdef-intersectionobserverinit, the IntersectionObserverInit.root should be of type Document | Element | null instead of just Element | null (https://github.com/microsoft/TypeScript/blob/v4.0.2/lib/lib.dom.d.ts#L638)

TypeScript Version: 4.0.2

Search Terms:
Intersection Observer, IntersectionObserverInit
Code

      const intersectionObserver = new IntersectionObserver(
        () => {},
        {
          root: document,
        }
      );

Expected behavior:
No error should be raised
Actual behavior:
See error:

TS2740: Type 'Document' is missing the following properties from type 'Element': assignedSlot, attributes, classList, className, and 58 more.

Playground Link:

Related Issues:

[troyt-42]

Fix here: microsoft/TypeScript-DOM-lib-generator#909