Document highlights on async/await keywords should highlight other occurrences in the same body

[DanielRosenwasser]

[|async|] function foo() {
  let x = [|await|] 100;
  let y = [|await|] 200;
  return 300
}

I'd expect each document highlight above to contain the others.

I wouldn't think the return keyword would be included here.

[mhegazy]

thanks @Zzzen!