Refactor FileIcon to styled-components

[manu-unter]

This is one of several smaller upcoming PRs with the goal to replace all remaining .less files with styled-components.

• Move the animation code from Tabs.less into FileIcon.tsx
• Replace additionalClassNames prop with the (also more restrictive, but better encapsulated) playAppearAnimation

[codecov]

Codecov Report

Merging #1980 into master will increase coverage by 0.02%.
The diff coverage is 45.45%.

@@            Coverage Diff             @@
##           master    #1980      +/-   ##
==========================================
+ Coverage   35.43%   35.46%   +0.02%     
==========================================
  Files         276      276              
  Lines       10617    10620       +3     
  Branches     1344     1343       -1     
==========================================
+ Hits         3762     3766       +4     
+ Misses       6670     6669       -1     
  Partials      185      185

Impacted Files	Coverage Δ
browser/src/UI/components/Tabs.tsx	33.33% <ø> (ø)	⬆️
browser/src/Services/FileIcon.tsx	57.14% <45.45%> (+20.77%)	⬆️

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[akinsho]

this looks great 👍

[bryphe]

👍 Thanks for splitting this out, @cryza !