Timeline in exams page

[pedroafmonteiro]

Closes #1452

Review checklist

• Terms and conditions reflect the current change
• Contains enough appropriate tests
• If aimed at production, writes a new summary in whatsnew/whatsnew-pt-PT
• Properly adds an entry in changelog.md with the change
• If PR includes UI updates/additions, its description has screenshots
• Behavior is as expected
• Clean, well-structured code

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 70 lines in your changes missing coverage. Please review.

Project coverage is 11%. Comparing base (780c535) to head (dbdf420).
Report is 48 commits behind head on ui/redesign.

Additional details and impacted files

@@             Coverage Diff              @@
##           ui/redesign   #1472    +/-   ##
============================================
- Coverage           11%     11%    -0%     
============================================
  Files              269     273     +4     
  Lines             7685    7821   +136     
============================================
- Hits               823     817     -6     
- Misses            6862    7004   +142