* support ToolIcon className and fix label padding
* factor some ExportDialog classes out to Modal
* initial RoomDialog prototype
* change label for another-session button
* remove unused css
* add color comments
* Move the collaboration button to the main menu, add support for mobile
* remove button for creating another session
* add locks
* Fix alignment issue
* Reorder button
* reuse current scene for collab session
* keep collaboration state on restore
Co-authored-by: Jed Fox <git@twopointzero.us>