Added some information about quickstart

[974650904]

默认的pip install "paddleocr>=2.0.1"在windows平台下，会下载paddleocr=2.0.1，然而，在2.0.1版本中不包含PP-OCRv4，所以调整了部分表述，减少初学者的疑惑。
修改范围包含中文和英文版本的 quickstart.md

Default pip install "paddleocr>=2.0.1" in windows, paddleocr=2.0.1 will be downloaded, however, PP-OCRv4 is not included in the 2.0.1 version, so some of the expressions are adjusted to reduce the confusion of beginners.
The modification scope includes the Chinese and English versions of quickstart.md

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[GreatV]

直接改成 pip install paddleocr 得了。

[jzhang533]

直接改成 pip install paddleocr 得了。

agree

[974650904]

直接改成pip install paddleocr得了。

可能我的经验不足，我觉得如果指定版本的话，可以降低维护指引Readme的频率，初学者可以简单的复现出结果。如果默认采用最新的版本，如果新版本中改变了调用方式，需要重写readme。仅为个人经验，如果不合适的话希望可以指导一下😊