Fix: custom fonts support on the Browser

[Dabolus]

Right now, it's not possible to embed custom fonts when generating a docx from a Browser without polyfilling Buffer because the obfuscator uses native Node.js Buffers without checking for their availability.

This PR makes the obfuscator use Uint8Arrays instead of Buffers, so that it can also work in the Browser without polyfilling.

I also renamed the related tests file because there was a small typo.

Resolves: #2667

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (e80a50d) to head (e8ffebc).

Additional details and impacted files

@@            Coverage Diff            @@
##            master     #2898   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          286       286           
  Lines         8370      8373    +3     
  Branches      1400      1400           
=========================================
+ Hits          8370      8373    +3     

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