Choose which person will stay on top, when many participants join (moderator feature)

[EnidKapelsen]

Goal: See the person talking, even if the group is getting bigger/more chaotic

Context: Can a participant get chosen/activated to stay "on top" / in the foreground. When many participants join, it gets quite crowded within the circle. As videos overlap it can be quite confusing to figure out who is speaking.

Additional Information: This feature request could also be solved in different other ways:

• If no overlays are possible
• If there is a "Redeobjekt" mechanism
• If the circle grows, when a group is growing

Related to #39