Do not encode HTML entities in JSON message files

[nicksnyder]

There is no reason <, >, or & need to be escaped in message files.

fixes #217

[codecov]

Codecov Report

Merging #228 into main will increase coverage by 0.24%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #228      +/-   ##
==========================================
+ Coverage   82.60%   82.85%   +0.24%     
==========================================
  Files          14       14              
  Lines        1173     1178       +5     
==========================================
+ Hits          969      976       +7     
+ Misses        142      140       -2     
  Partials       62       62              

Impacted Files	Coverage Δ
v2/goi18n/marshal.go	86.11% <100.00%> (+8.69%)	⬆️

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