Create dummy type definitions for 3rd party modules if none are installed

[AlCalzone]

This should avoid questions like https://forum.iobroker.net/topic/34220/problem-zus%C3%A4tzliche-module-f%C3%BCr-javascript-nicht-verf%C3%BCgbar

[AlCalzone]

Turns out, it is as easy as this:

declare module "foo";