update to use async/await

[minrk]

Proposed change

Now that we've updating things to more modern js, we can update all our code to use async/await instead of promises.

This should have no user-facing or compatibility effects, since promises and async/await are equivalent. Just an aesthetic/maintenance improvement since chaining promises is annoying and complicated.

Since this is not a very active development project, improvements to maintenance aren't that valuable, so this should be a low priority, but if anyone feels like some tedious refactoring should feel welcome.

Alternative options

Leave it alone, since refactors can introduce bugs.

Who would use this feature?

Maintainers/contributors only.

(Optional): Suggest a solution

I don't know if there are any refactor tools that can give us a starting point automatically?