Allow subbing in JSDOM for use in node

[lajoiemedia]

Exports a new function called setWindowObject which sets a singleton windowObject.

All references to window are now replaced with this windowObject, e.g. windowObject.document or windowObject.NodeList.

That way we can do setWindowObject(new JSDOM("").window) after import so that htl can be used in node.

windowObject defaults to globalThis.window, so no code changes will be needed for browser usage.