[Beta Feedback] Adjust Bubble Density

**Is your feature request related to a problem? Please describe.**

I gave the new bubble view a try today. It looks great on mobile, though, on Web/Desktop it leaves a lot of white space.

**Describe the solution you'd like**

Some messaging clients have the ability to adjust the density of messages. I think this would help improve the efficiency of viewing messages.

**Describe alternatives you've considered**

The obvious alternative is sticking with the text-based view.

Start by locating the new bubble view in the Element Web codebase and review how its Web/Desktop layout differs from the mobile presentation. Define the supported message-density options and confirm that the bubble view can reduce excess white space without changing the existing text-based view.

Written by the indexing model from the issue text.