Window type is not documented

Type of `Window`, `NodeList` and likely other interesting types are not mentioned in [the wiki](https://github.com/google/closure-compiler/wiki/Types-in-the-Closure-Type-System).

Since not all types are supported (e.g. `HTMLCanvasElement`, etc. see #4028), it would be useful to know what types are meaningfully supported by the compiler and what types are simply considered `unknown`.