[Feature] Overload waitForEvent to return specific type

[kalekseev]

Right now waitForEvent return type is Object, but we can have specific types with overload:

waitForEvent(event: "popup", optionsOrPredicate?: Function|PageWaitForEventOptionsOrPredicate): Promise<Page>;
...
waitForEvent(event: string, optionsOrPredicate?: Function|PageWaitForEventOptionsOrPredicate): Promise<Object>;

[pavelfeldman]

I thought we already had it. I can see specializations in my working folder types/types.d.ts, but not in the playwright-core@next. @JoelEinbinder do you know what is going on here?

[JoelEinbinder]

I misspoke, the PR seems to have gotten lost in the mail. Thanks for catching this!