Allow loops containing await

[joshski]

Hi!

I found this plugin handy... but I don't mind loops with awaits in them, e.g.

for (const foo of foos) {
  await foo()
}

...because this is a neat way of expressing serial execution of a list of async things (compared to say, using reduce).

But I'm not sure if this would warrant spawning a new plugin (e.g. no-sync-loops), or an option for this one. What do you think?