NodeListOf#item misses return type "null"

[danielrentz]

Interface NodeList is correctly typed

interface NodeList {
    item(index: number): Node | null;
}

but interface NodeListOf is missing the null type:

interface NodeListOf<TNode extends Node> extends NodeList {
    item(index: number): TNode;
}

therefore TSC does not warn about missing null checks:

const node = document.childNodes.item(999999).firstChild;

[orta]

~~Agree 👍🏻 open to changes here~~

Changed my mind after thinking about it in https://github.com/microsoft/TypeScript-DOM-lib-generator/pull/1268, this is probably too big of an ecosystem break