Taskbar progress indicator on long running commands

[Antaris]

Description of the new feature/enhancement

Windows allows for the identification of long running processes via a progress indicator on a taskbar button of the active application.

I often find myself waiting for commands to complete (e.g. a yarn build, or some other long running process) in the terminal, and frequently end up tabbing between apps just to check if something is complete.

I'd really like an option in Windows terminal to activate a progress indicator for commands that have been running over n seconds. This should use the existing Windows APIs to display an infinite progress bar until the command has completed. I don't know a finite progress bar is possible without commands being explicitly aware they are running via the terminal.

Obviously if there are multiple tabs perhaps the progress indicator could flash across the taskbar (to signal that something is executing, but if the terminal is open, the "in progress" tab could have a similar mechanism?

[Antaris]

Actually, this is a dupe of #3004