async/delay DelayOptions should take an unref boolean

With the new Deno.unrefTimer support in Deno v1.17, the DelayOptions interface for async/delay.ts should support a new boolean field unref

When unref is set to true, the id of the internal setTimeout should be automatically unreffed with Deno.unrefTimer(i)

Thus a call like this:

await delay(1000, {unref : true});

wouldn’t prevent Deno from exiting.

[iuioiua]

@kt3k, I believe this issue can be closed.

[kt3k]

@iuioiua

doing this will break browser compatibility unless a Deno namespace check is done.

Right, let’s check Deno namespace and keep the browser compatibility.