Update gif demo (#3924)
Update gif demo (#3924)

Include parallel writing with two users
ether/etherpad-lite,storytouch/etherpad-lite,storytouch/etherpad-lite,joequant/etherpad-lite,ether/etherpad-lite,storytouch/etherpad-lite,joequant/etherpad-lite,joequant/etherpad-lite,joequant/etherpad-lite,ether/etherpad-lite