Add ViewComponent for progressbar

What does this MR do and why?

Adds a new ViewComponent for progress bars.

Screenshots or screen recordings

No visual change.

How to set up and validate locally

• See the component in use at http://gdk.test:3000/dashboard/milestones (in every row of that index page)
• Click on any milestone. The component is also used in the milestone sidebar on the right.
• Checkout the component preview at http://gdk.test:3000/rails/lookbook/inspect/pajamas/progress/default

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.