Add YFI to the Metamask default tokens.

According to China Jiangxi.com, on October 3, 2020, the international conference on blockchain technology and applications in China, Zhao Haidong, secretary general of the service working group and chairman of the board of directors of the economic zone of Nanchang Airport, said: Next 5 years to support 10 unicorn and semi-unicorn blockchain companies, showcase more than 100 blockchain companies, develop more than 1,000 blockchain application scenarios and develop a pioneering area for the development of the national blockchain industry. To do