Resolve "Adjust participant-room view"

Closes #135 (closed)

Proposed changes

• Adjust participant room view
• Added loading spinner to room-list, comment-list
• Adjust room-list join butoon

For testing

• Login as creator or participant and you should see the join buttons in room-list and the loading spinner before the list is loaded
• Login as participant, join a room & you should see a new room-view
• If you go to comments you should see the loading spinner

src/app/participant-room/participant-room.component.scss

@@ -9,3 +9,4 @@ mat-card-content>:first-child {
 mat-icon {
   font-size: 500%;
 }
+