Ask HN: Easy way to save files from web app to cloud?

I have a Java desktop app to create/edit files that I ported to the browser/JavaScript with TeaVM. What is the easiest way to save files from a web app to the cloud?

I'm looking for a shortcut right now - ideally, I'd like to be able to save the file with a simple HTTP POST, then retrieve the file with HTTP GET. I'm hoping I can use a public service like DropBox/OneDrive/GoogleDrive (setting up my own AWS S3 server is a job for another day).

I was just hoping someone might have some ideas/insight.