Add Letvcloud support, as in #422

Have to redo this sh*t for 3 times due to the stupidity of the damned
editor and Git. FML.
fix 3c9a774 to get everything works
remove unused _letvcloud.py
AcFun: fix #422
NetEase: fix #428
add douyutv support.
fix douyutv support.
fix douyutv support.
fix douyutv title regex
support live.bilibili.com
douyutv.com now can download online flv.
	modified:   common.py
	modified:   extractors/douyutv.py
	modified:   extractors/bilibili.py
Add Letvcloud support, as in #422

Have to redo this sh*t for 3 times due to the stupidity of the damned
editor and Git. FML.
Merge branch 'merge-main' into develop

Conflicts:
	src/you_get/common.py
--fix