Add static builder method for json transformer

[snuyanzin]

Simplify invocation of json transformer builder in the same way like it is already done for sql transformer:
static builder method

[codecov-commenter]

Codecov Report

Merging #669 (2664499) into main (c4b6674) will increase coverage by 0.01%.
The diff coverage is 100.00%.

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@@             Coverage Diff              @@
##               main     #669      +/-   ##
============================================
+ Coverage     92.74%   92.76%   +0.01%     
- Complexity     2634     2635       +1     
============================================
  Files           283      283              
  Lines          5429     5430       +1     
  Branches        590      590              
============================================
+ Hits           5035     5037       +2     
+ Misses          244      243       -1     
  Partials        150      150              

Impacted Files	Coverage Δ
.../java/net/datafaker/service/FakeValuesService.java	85.03% <100.00%> (ø)
...net/datafaker/transformations/JsonTransformer.java	95.61% <100.00%> (+0.03%)	⬆️
...n/java/net/datafaker/providers/base/BaseFaker.java	87.82% <0.00%> (-0.87%)	⬇️
.../datafaker/transformations/sql/SqlTransformer.java	88.19% <0.00%> (+0.73%)	⬆️

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