[basicdataset] Add PennTreebank dataset

[AKAGIwyf]

Description

Add a version of Penn Treebank which is free on github but without POS tags as Torchtext, it had been pre-processed.

close #1579.

[zachgk]

Thanks for the changes. I made a small change to fix the license. If you haven't done much with licenses, the Apache2 license is typically used for code but there are different licenses used for other kinds of content (books, movies, documents, papers, datasets, artwork, etc). It is important to get the license right and follow the terms because the license describes what you are legally allowed to do with the content.

Besides that, the metadata is uploaded, so you can not modify your tests to use the DJL central repository instead of the local repository.

[codecov-commenter]

Codecov Report

Merging #1580 (8ece361) into master (bb5073f) will decrease coverage by 1.21%.
The diff coverage is 53.04%.

@@             Coverage Diff              @@
##             master    #1580      +/-   ##
============================================
- Coverage     72.08%   70.87%   -1.22%     
- Complexity     5126     5427     +301     
============================================
  Files           473      507      +34     
  Lines         21970    23757    +1787     
  Branches       2351     2587     +236     
============================================
+ Hits          15838    16837     +999     
- Misses         4925     5630     +705     
- Partials       1207     1290      +83     

Impacted Files	Coverage Δ
api/src/main/java/ai/djl/modality/cv/Image.java	69.23% <ø> (-4.11%)	⬇️
...i/djl/modality/cv/translator/BigGANTranslator.java	21.42% <ø> (-5.24%)	⬇️
...odality/cv/translator/BigGANTranslatorFactory.java	33.33% <0.00%> (+8.33%)	⬆️
...nslator/InstanceSegmentationTranslatorFactory.java	14.28% <0.00%> (-3.90%)	⬇️
.../modality/cv/translator/YoloTranslatorFactory.java	8.33% <0.00%> (-1.67%)	⬇️
...i/djl/modality/cv/translator/YoloV5Translator.java	5.69% <0.00%> (ø)
...odality/cv/translator/YoloV5TranslatorFactory.java	8.33% <0.00%> (-1.67%)	⬇️
...pi/src/main/java/ai/djl/ndarray/BytesSupplier.java	54.54% <0.00%> (-12.13%)	⬇️
...pi/src/main/java/ai/djl/repository/Repository.java	83.33% <ø> (ø)
...l/training/loss/SigmoidBinaryCrossEntropyLoss.java	64.00% <0.00%> (ø)
... and 243 more

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