Please provide support for mobile browsers

[vkuznet]

Hi, I'm working on application for mobile and use rclone library to sync files from cloud providers. The rclone library depends on yours, and uses to open OAuth requests to upstream provider. Since there is no support for mobile within your library I can't proceed using rclone. I would really appreciate if you'll add support to open urls in mobile environment. I know that it is possible since I'm using fyne.io For example, you can see how they are doing open call for android and ios.