Resolve "Follow-up from "Resolve "creator home screen - room logic (room)"""

Closes #87 (closed)

Proposed changes

• Deletion dialog is now shown as matdialog popup using the view of room-deletion component

Testing

• Login as creator
• join a room
• delete a room -> you should see the deletion-confirm-popup
• choose 'delete room' -> you should see the room list without the deleted room