Make intro page more informative of the task

[JamesPHoughton]

Currently, participants see a screen before they enter the discussion that tells them what they are going to see. There are a number of things we could add to this page to give the participants more situational awareness, including:

• [ ] Add a screenshot of the discussion page, with arrows pointing out prompts, mute buttons, etc. (requires: https://github.com/Watts-Lab/deliberation-empirica/issues/520)
• [ ] Play the prompt transition chime so that people know what it means when they hear it (Relates to: https://github.com/willschulz/bad-influence/issues/11)

Other ideas?

[willschulz]

Additional idea: have them watch a very brief video (30 seconds) that gives a tutorial re: discussion interface and discussion question transitions.