it('add should return removal function', () => {
   const signal = new Signal();
   let result = '';
   const removalFunction = signal.add(() => {
     result += 'a';
   });
   signal.dispatch();
   expect(result).toEqual('a');
   expect(removalFunction()).toEqual(true);
   signal.dispatch();
   expect(result).toEqual('a');
   expect(removalFunction()).toEqual(false);
 });

export function addSignalBinding<T extends Function>(signal: Signal<T>, handler: T) {
  signal.add(handler);
}

 const handler1 = () => {
   result += 'a';
   signal.remove(handler2);
 };