Scope of the task force

[xfq]

https://github.com/w3c/danmaku/blob/master/TF/Bullet_Chatting_TF_Draft.md

Currently the scope is "TBD". We should make it clear.

[flyingzl]

Since we have clarified the priority in the last TF meeting that we'll focus on the rendering capability for Bullet Chatting , so an available scope is :

The Task Force aims to propose and discuss technical details of the rendering capability 
for Bullet Chatting which will involve these following scenarios:

- on-demand video scenario
- live streaming scenario
- non-video scenario

any ideas?