Add global variables in typescript

In this example, we need to put placeholder values on global.window to allow us to use Ruby on Rails' ActionCable websocket framework where no window exists:

// Fix to prevent crash from ActionCable
global.window.removeEventListener = () => {};
global.window.addEventListener = () => {};

But we need to add a type:

declare global {
    var window: {
        addEventListener(): void;
        removeEventListener(): void;
    };
}