[Docs] yolov5_description.md in English (#198)

* draft 1 yolov5_descrip_eng

* Update docs/en/algorithm_descriptions/yolov5_description.md

Co-authored-by: HinGwenWoong <peterhuang0323@qq.com>

* Update docs/en/algorithm_descriptions/yolov5_description.md

Co-authored-by: HinGwenWoong <peterhuang0323@qq.com>

* Update docs/en/algorithm_descriptions/yolov5_description.md

Co-authored-by: HinGwenWoong <peterhuang0323@qq.com>

* add section 1.3

* draft finished

* update docs

* Update docs/en/algorithm_descriptions/yolov5_description.md

Co-authored-by: HinGwenWoong <peterhuang0323@qq.com>

* remove unnecessary parts

* Update docs/zh_cn/algorithm_descriptions/yolov5_description.md

Co-authored-by: Range King <RangeKingHZ@gmail.com>

* Update docs/en/algorithm_descriptions/yolov5_description.md

Co-authored-by: Range King <RangeKingHZ@gmail.com>

* Update docs/en/algorithm_descriptions/yolov5_description.md

Co-authored-by: Range King <RangeKingHZ@gmail.com>

* Update docs/en/algorithm_descriptions/yolov5_description.md

Co-authored-by: Range King <RangeKingHZ@gmail.com>

* Update docs/en/algorithm_descriptions/yolov5_description.md

Co-authored-by: Range King <RangeKingHZ@gmail.com>

* Update docs/en/algorithm_descriptions/yolov5_description.md

Co-authored-by: Range King <RangeKingHZ@gmail.com>

* Update docs/en/algorithm_descriptions/yolov5_description.md

Co-authored-by: Range King <RangeKingHZ@gmail.com>

* Update docs/en/algorithm_descriptions/yolov5_description.md

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* open-sourced -> open-source

* merge&update

* assignment strategy&merge dev branch

Co-authored-by: HinGwenWoong <peterhuang0323@qq.com>
Co-authored-by: Range King <RangeKingHZ@gmail.com>