[examples] update pose estimation example to detect joints for all people

[siddvenk]

Description

While working on the serving example for human detection + pose estimation, I noticed that the djl example could use an update to detect joints for all people in the image instead of just a single person. I also fixed a small typoin the documentation.

[codecov-commenter]

Codecov Report

Merging #2002 (2b71318) into master (bb5073f) will decrease coverage by 2.18%.
The diff coverage is 68.82%.

@@             Coverage Diff              @@
##             master    #2002      +/-   ##
============================================
- Coverage     72.08%   69.90%   -2.19%     
- Complexity     5126     5917     +791     
============================================
  Files           473      586     +113     
  Lines         21970    26216    +4246     
  Branches       2351     2846     +495     
============================================
+ Hits          15838    18325    +2487     
- Misses         4925     6511    +1586     
- Partials       1207     1380     +173     

Impacted Files	Coverage Δ
api/src/main/java/ai/djl/modality/cv/Image.java	69.23% <ø> (-4.11%)	⬇️
...rc/main/java/ai/djl/modality/cv/MultiBoxPrior.java	76.00% <ø> (ø)
...rc/main/java/ai/djl/modality/cv/output/Joints.java	71.42% <ø> (ø)
.../main/java/ai/djl/modality/cv/output/Landmark.java	100.00% <ø> (ø)
...main/java/ai/djl/modality/cv/output/Rectangle.java	72.41% <0.00%> (ø)
...i/djl/modality/cv/translator/BigGANTranslator.java	21.42% <0.00%> (-5.24%)	⬇️
...odality/cv/translator/BigGANTranslatorFactory.java	33.33% <0.00%> (+8.33%)	⬆️
.../cv/translator/InstanceSegmentationTranslator.java	0.00% <0.00%> (-86.59%)	⬇️
...nslator/InstanceSegmentationTranslatorFactory.java	7.14% <0.00%> (-11.04%)	⬇️
.../cv/translator/SemanticSegmentationTranslator.java	0.00% <0.00%> (ø)
... and 499 more

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