[rtcweb] Use Case draft

[Ted Hardie <[e-mail]>]

The chairs would like to ask the working group to focus on the use
case draft.  If you have use cases that need to be added to the
document or text changes you'd like to suggest, please send them in
for discussion before May 15th.  After this round, we will look toward
having a working group last call on the document (hopefully before the
interim meeting).

regards,

Ted, Magnus, Cullen