Peeking has regressed and isn't skinned properly

[ara4n]

We no longer have a MemberList when peeking.

Also, we have the oldschool lozenge buttons for Login & Register. Instead, this should be skinned to match the designs in zeplin.

[t3chguy]

Lack of memberlist: matrix-org/matrix-react-sdk@dd911d1

[turt2live]

The memberlist seems intentional now: #10769

[t3chguy]

Closing as matches design