Add new JSON generation example in file formats docs

[panilya]

Issue: #346

[codecov-commenter]

Codecov Report

Merging #354 (2ef2ed2) into main (03ceb70) will decrease coverage by 0.05%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##               main     #354      +/-   ##
============================================
- Coverage     94.85%   94.80%   -0.06%     
+ Complexity     1935     1934       -1     
============================================
  Files           203      203              
  Lines          3869     3869              
  Branches        385      385              
============================================
- Hits           3670     3668       -2     
- Misses          101      102       +1     
- Partials         98       99       +1     

Impacted Files	Coverage Δ
...ker/idnumbers/pt/br/IdNumberGeneratorPtBrUtil.java	92.59% <0.00%> (-3.71%)	⬇️

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[snuyanzin]

Since it is example of simple JSON generation I think it would make sense to place it at the very beginning of JSON section and then more complex examples