Add various dataset examples

[illian01]

Description

Please include a summary of this pull request in English. If it closes an issue, please mention it here.

Closes: #404

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Change(s)

• Add automatic dataset format converter
  • cifar100, imagenet1k, coco2017, voc2012
• Update README.md
  • Add contents about dataset preparation
• Update docs
  • Add dataset preparation scenarios in getting_started
  • Fix contents in components/data.md

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