To-do: Help put together the AR face-to-face topics

Hello, immersive web people.

If you're attending the September 17th AR face-to-face in person or
remotely then please take a look at this spreadsheet
<https://docs.google.com/spreadsheets/d/1ivxcQIjMxuvhnYpVxFTh0kGNoYxx-S0SGPP-W8S5ZW8/edit?usp=sharing>
and help us gather topics.

If there are missing topics that you'd like to address then add them to the
bottom of the list.

On the right hand side, add a column with your name at the top and vote
whether you consider each topic to be "required" or "optional".

On Monday, we'll gather the results and put together the schedule with
links to the relative Issues and PRs.

Thanks for your help!

- Trevor