Add Sougou Browser detection

[itsalongstory]

SOUGOU_BROWSER: "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.81 Safari/537.36 SE 2.X MetaSr 1.0"
SOUGOU_BROWSER_MOBILE: "Mozilla/5.0 (Linux; Android 7.1.2; Redmi 4X Build/N2G47H; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/68.0.3440.106 Mobile Safari/537.36 AWP/2.0 SogouMSE,SogouMobileBrowser/5.28.12"

https://ie.sogou.com/

Sogou desktop browser is very popular in mainland China.