Enable yahoo finance api for Chinese users

[Newtype07]

Description

Yahoo finance is not available for Chinese users for years, there has been always Http error 403 after calling getSymbols even if proxies are used to access foreign websites. However, directly requesting Yahoo finance api seems possible following instructions on this website: https://cryptocointracker.com/yahoo-finance/yahoo-finance-api

Expected behavior

Enable yahoo finance api for Chinese users by adding functionalities to request Yahoo finance api and parse the .json data to R objects, so that functions such as getSymbols can be used in China.

Thanks a lot.