Additional TPAC connection information

In today's COGA teleconference, there were a few questions I didn't know 
the answers to:

  * Can presenters join sessions early
  * How does the 2-step registration work
  * How should presenters share slides

It turns out we will be using Zoom for the sessions. The event platform 
can create calls for us, but they will be available only 5 minutes 
before the session. But we are also able to schedule our own Zoom call 
and use that instead, in which case we will know the connection 
information well in advance. I will work with staff to get that set up, 
so we should be able to provide Zoom coordinates in advance, and share 
slides as we normally do.

The two-step registration boils down to:

 1. Register at https://www.w3.org/register/tpac2021virtual
 2. Receive an automated email response.
 3. Wait up to a few days for a second email from "W3C Events Team" and
    subject "Welcome to TPAC 2021". This unimportant-sounding message
    indicates you have been authorized for the second registration step.
 4. Go to https://eur.cvent.me/yGw02 to register into the event
    platform, via a verification code. /You will need to go to that URI
    once every 24 hours/ to refresh your registration, there is no login
    link on the meeting pages.
 5. To get to the event platform, start at
    https://www.w3.org/2021/10/TPAC/format.html and search for "schedule
    is now available". These unpromising links are the entries to the
    event platform. There is one link for the breakout sessions next
    week, another one for group meetings the following week.

The following resources kinda sorta document this process:

  * https://www.w3.org/2021/10/TPAC/format.html#intro
  * https://docs.google.com/document/d/19p6cA_TdMZ8yVQ_qBQITjfbLgeJ9KD3LK-LdlaR2ieA/edit

Michael