Support async formatter

[Oscaner]

Problem to solve What kind of problem you were trying to solve when you realized there is a missing feature?

What works How close to your goal you can currently get?

What is missing What prevents you from achieving your goal?

How the missing feature should be implemented Explain any technical details here.

Bigger picture Do you think this feature has different uses? Is there a better way to do it? What other options you've considered?