Update dom.js: change NodeList to NodeList<HTMLElement>

[ptmt]

There is a problem with code like this:

document.querySelectorAll('.selector')[0].style.display = 'block';

because querySelectorAll returns NodeList of Element, not Node https://developer.mozilla.org/en-US/docs/Web/API/element.

I've changed NodeList to NodeList<T> and signatures of some relevant functions:

querySelector(selector: string): HTMLElement;
querySelectorAll(selector: string): NodeList<HTMLElement>;

though HTMLElement is no exactly correct (it could be any of derived classes of Element such as SVGElement, for example) I don't know better solution.
Also, there is inconsistency with HTMLCollection which is collection of Element and will produce error with code sample.

[ptmt]

Sorry for these unserious and unrelevant pull requests, may be #151 helps a bit to avoid such repetitive issues.

[gabelevi]

Cool, this looks good to me!