Creating generic squircle container

[AugustoVSoares]

Closes #1451

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 11%. Comparing base (7d074d2) to head (b1e5ba2).
Report is 1 commits behind head on ui/redesign.

❌ Your project check has failed because the head coverage (11%) is below the target coverage (70%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff             @@
##           ui/redesign   #1454   +/-   ##
===========================================
  Coverage           11%     11%           
===========================================
  Files              270     270           
  Lines             7358    7358           
===========================================
  Hits               807     807           
  Misses            6551    6551