[Console] Add documentation for `ProgressIndicator`

[welcoMattic]

We have a ProgressIndicator in Console component for years (almost 10!), but no documentation about it. It could easily be used as spinner to display progression of task without a predictable number of elements.

Code: https://github.com/symfony/symfony/blob/6.4/src/Symfony/Component/Console/Helper/ProgressIndicator.php

[alexandre-daubois]

Having a look 🙂