Add information on progress bars

[janfaracik]

Added some short information on when to use certain progress related components. Relates to jenkinsci/jenkins#8821

Testing done

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1. Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
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3. Please describe what you did
4. Link to relevant issues in GitHub or Jira
5. Link to relevant pull requests, esp. upstream and downstream changes
6. Ensure you have provided tests - that demonstrates feature works or fixes the issue

[NotMyFault]

Thanks!