test(dtslint): add fromEvent dtslint test (ReactiveX#4093)

spec-dtslint/observables/fromEvent-spec.ts

@@ -0,0 +1,20 @@
+import { fromEvent } from 'rxjs';
+import { NodeStyleEventEmitter, HasEventTargetAddRemove } from '../../src/internal/observable/fromEvent';
+
+const hasEventTargetAddRemove: HasEventTargetAddRemove<string> = {
+  addEventListener: (type, listener, options?) => { },
+  removeEventListener: (type, listener, options?) => { }
+};
+
+const nodeStyleEventEmitter: NodeStyleEventEmitter = {
+  addListener: (eventName, handler) => nodeStyleEventEmitter ,
+  removeListener: (eventName, handler) => nodeStyleEventEmitter
+};
+
+it('should infer correctly with HasEventTargetAddRemove event type', () => { 
+  const a = fromEvent(hasEventTargetAddRemove, 'foo'); // $ExpectType Observable<string>
+});
+
+it('should infer correctly with NodeStyleEventEmitter event type', () => {
+  const a = fromEvent(document, 'foo'); // $ExpectType Observable<Event>
+});