fix: align IntersectionObserver options with DOM API

src/index.tsx

@@ -21,7 +21,7 @@ interface RenderProps {
 
 export interface IntersectionOptions extends IntersectionObserverInit {
   /** The IntersectionObserver interface's read-only `root` property identifies the Element or Document whose bounds are treated as the bounding box of the viewport for the element which is the observer's target. If the `root` is null, then the bounds of the actual document viewport are used.*/
-  root?: Element | null;
+  root?: Element | Document | null;
   /** Margin around the root. Can have values similar to the CSS margin property, e.g. `10px 20px 30px 40px` (top, right, bottom, left). */
   rootMargin?: string;
   /** Number between `0` and `1` indicating the percentage that should be visible before triggering. Can also be an `array` of numbers, to create multiple trigger points. */