New bottom navbar

[Process-ing]

Closes #1267

It adds the new bottom navbar. To use it, the app needs to provide the navbar items, along with their icons and desired behaviors.

I also added a slight splash effect when clicked. If you think it should be removed, let me know.

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 (9acce2d) to head (8c6e3cc).
Report is 5 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #1306   +/-   ##
=======================================
  Coverage       11%     11%           
=======================================
  Files          269     269           
  Lines         7345    7345           
=======================================
  Hits           802     802           
  Misses        6543    6543