[ACA-3899] Viewer thumbnails cannot be accessed by keyboard

[pionnegru]

Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (check one with "x")

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation
• Other... Please describe:

What is the current behaviour? (You can also link to an open issue here)
ACA-3899

What is the new behaviour?

Does this PR introduce a breaking change? (check one with "x")

• Yes
• No

If this PR contains a breaking change, please describe the impact and migration path for existing applications: ...

Other information:

[codecov-commenter]

Codecov Report

Merging #6150 into develop will increase coverage by 1.32%.
The diff coverage is 97.61%.

@@             Coverage Diff             @@
##           develop    #6150      +/-   ##
===========================================
+ Coverage    75.35%   76.68%   +1.32%     
===========================================
  Files          624      843     +219     
  Lines        14849    18882    +4033     
  Branches      3119     3746     +627     
===========================================
+ Hits         11190    14479    +3289     
- Misses        2718     3260     +542     
- Partials       941     1143     +202     

Impacted Files	Coverage Δ
...ewer/components/pdf-viewer-thumbnails.component.ts	96.38% <96.87%> (-0.17%)	⬇️
...re/viewer/components/pdf-viewer-thumb.component.ts	100.00% <100.00%> (ø)
lib/core/viewer/components/pdf-viewer.component.ts	83.42% <100.00%> (-0.47%)	⬇️
...b/core/context-menu/context-menu-list.component.ts	50.00% <0.00%> (-5.56%)	⬇️
...ib/document-list/services/document-list.service.ts	74.50% <0.00%> (-1.97%)	⬇️
lib/extensions/src/lib/config/extension-utils.ts
...b/extensions/src/lib/services/extension.service.ts
lib/extensions/src/test.ts
...b/extensions/src/lib/evaluators/core.evaluators.ts
... and 234 more

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