Fix: firefox thumb active state

[MurhafSousli]

Closes #709

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (010cb4b) to head (43057b0).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #710   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           28        28           
  Lines          765       781   +16     
  Branches       164       166    +2     
=========================================
+ Hits           765       781   +16     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[github-actions]

Package	Line Rate	Branch Rate	Health
reached-event.src	100%	82%	✔
src.lib	100%	85%	✔
src.lib.button	100%	82%	✔
src.lib.scrollbar	100%	95%	✔
src.lib.scrollbars	100%	100%	✔
src.lib.tests	100%	100%	✔
src.lib.thumb	100%	95%	✔
src.lib.track	100%	97%	✔
src.lib.utils	100%	95%	✔
src.lib.viewport	100%	70%	✔
Summary	100% (644 / 644)	84% (321 / 380)	✔

Minimum allowed line rate is 60%