Feature/empty state illustrations

[GuiCNunes]

Closes #639
Empty state ilustrations for schedule and exams cards.

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

All modified and coverable lines are covered by tests ✅

Project coverage is 12%. Comparing base (92e33f6) to head (ad891f9).
Report is 1 commits behind head on ui/redesign.

Additional details and impacted files

@@             Coverage Diff             @@
##           ui/redesign   #1415   +/-   ##
===========================================
+ Coverage           12%     12%   +1%     
===========================================
  Files              265     265           
  Lines             7209    7203    -6     
===========================================
+ Hits               806     808    +2     
+ Misses            6403    6395    -8     

[thePeras]

The code is almost perfect.
Leave us some screenshots to see the results, please

[thePeras]

use translations

[thePeras]

use translations