[Pas2js] Async, AWait

[Michael Van Canneyt]

On Mon, 1 Jun 2020, Mattias Gaertner via Pas2js wrote:

> On Mon, 1 Jun 2020 10:17:07 +0200 (CEST)
> Michael Van Canneyt <michael at freepascal.org> wrote:
>
>> On Sun, 31 May 2020, warleyalex via Pas2js wrote:
>> 
>> > Nice!
>> >
>> > The Sleep method is missing in pa2js! This method is very useful, I
>> > think it should live at sysutils unit. 
>> 
>> A nice idea.
>
> Maybe choose another name?
> Sleep() without await will return immediately and code ported from
> Delphi/FPC won't notice the problem.

Well, they need to add the webutils unit, so they will need to be aware.
But as a precaution, I changed the name to asyncsleep.

Michael.