Add a status icon for muted room on RoomListPage

This could be helpful for some working use-case: When user want to mute a channel temporary and want to un-mute it later, the icon could help user know the mute status at a glance so they won't forget to un-mute the channel.

This icon will only be shown if the channel is muted, and have no unread message and the item is not hovered, so it won't get in the way when user have unread messages.