Allow users to hide rooms with specific tags

resources/styles/nheko-dark.qss

resources/styles/nheko.qss

resources/styles/system.qss

src/ChatPage.cpp

src/CommunitiesList.cpp

src/CommunitiesList.h

src/CommunitiesListItem.cpp

src/CommunitiesListItem.h

src/MatrixClient.cpp

src/RoomInfoListItem.cpp

src/RoomInfoListItem.h

src/RoomList.cpp

src/RoomList.h