Add docs on how progress bar sequence works #514

From #12590. See #6700 for the mega thread.

We don't really have any docs on how commandline apps can set the progress bar state. Maybe we should! That's a new feature in the Terminal, so we should help clue users into that. Also refer to winget, since that's a good example of an app already using this.

Maybe under Tutorials?

We should probably also include that sequence over at https://github.com/MicrosoftDocs/Console-Docs as well.

Probably also include reference to how the "glomming" works, as noted in microsoft/terminal#6700 (comment)