[stable30] fix(files): Add smooth animation via clicking on heading

[backportbot]

Backport of #7197

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 51.36%. Comparing base (f94237c) to head (6bcf87b).
Report is 2 commits behind head on stable30.

Files with missing lines	Patch %	Lines
src/plugins/headingAnchor.js	0.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           stable30    #7319      +/-   ##
============================================
- Coverage     51.38%   51.36%   -0.02%     
============================================
  Files           116      116              
  Lines          2709     2710       +1     
  Branches        542      542              
============================================
  Hits           1392     1392              
  Misses         1189     1189              
- Partials        128      129       +1     

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