Move reddit.com asset URL fix to SanitizeAssetsOutlinks

[vbanos]

Addressing issue #397

Also add unit test.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 66.66667% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 55.59%. Comparing base (dc1cc5b) to head (38a2abd).
⚠️ Report is 120 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/pkg/postprocessor/assets.go	66.66%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #416      +/-   ##
==========================================
+ Coverage   55.17%   55.59%   +0.42%     
==========================================
  Files         117      119       +2     
  Lines        7257     7301      +44     
==========================================
+ Hits         4004     4059      +55     
+ Misses       2935     2919      -16     
- Partials      318      323       +5     

Flag	Coverage Δ
e2etests	37.42% <0.00%> (-0.18%)	⬇️
unittests	31.97% <66.66%> (+0.83%)	⬆️

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[NGTmeaty]

Thanks!