Fix website's yarn start on Windows

[ndresx]

Summary
This PR fixes a problem with the website's launching sequence on Windows when running yarn start. In some cases it seems to be necessary to replace the \n character with the OS' specific one through node's os.EOL constant because the \r character remains if just \n gets replaced on a Windows (10) machine.

The change in feed.js (TypeError: Cannot read property '1' of null) actually brings the site back up whereas the change in convert.js displays the blog post preview texts (not displayed without the change).

Test plan
N/A, only clicked it through on a Windows and Mac.

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[codecov-io]

Codecov Report

Merging #3510 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3510   +/-   ##
=======================================
  Coverage   62.28%   62.28%           
=======================================
  Files         181      181           
  Lines        6700     6700           
  Branches        5        5           
=======================================
  Hits         4173     4173           
  Misses       2525     2525           
  Partials        2        2

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