update team leader onboarding to support current workshop setup

[samumantha]

• replace hackmd with collaborative doc
• breakout room/session mentions are now less zoom specific
• replace mentions of "asking helpers to room" to "put question on collaborative document"

Zoom setup still mentioned in "background:teams" as "sometimes we also allow learners... ", other than that I did not quite find a reason to have a separate page for CR offered zoom room vs only self-organized teams. So no separate new page for now.

The new screenshot is missing the annotations, but maybe they are not needed? If you think they are, can still add them

[samumantha]

Draft because: One page that is linked often, is hackmd-machanics , will do some updates there to call it collaborative doc, but leave the file name to not break other links for now.

[samumantha]

resolves #213

[rkdarst]

Looks pretty good to me. I would have more updates later, but that can be separate

[bast]

Thanks a lot for this work.