* add install of paddleclas

* update inference with paddlecv

* add PP-OCRv2

* add PP-OCRv2 benckmark

* update app

* update introduction

* update PP-OCRv2 introduction

* add pipeline of PP-OCRv2

* add PP-OCRv3

* update benckmark

* add paddleocr to requirements

* update

* support paddleocr 2.6.0.1

* rm print code

* add image download

* add model train

* update PP-OCRv3 ref

* update doc

* update doc

* update PP-OCR info

* add PP-StructureV2

* update doc

* merge upstream

* update info.yaml