Group emoji and dialogs with namespaces

CMakeLists.txt

include/RoomList.h

include/TextInputWidget.h

include/TopRoomBar.h

include/UserInfoWidget.h

include/dialogs/ImageOverlay.h

include/dialogs/JoinRoom.h

include/dialogs/LeaveRoom.h

include/dialogs/Logout.h

include/emoji/Category.h

include/emoji/ItemDelegate.h

include/emoji/Panel.h

include/emoji/PickButton.h

include/emoji/Provider.h

resources/styles/nheko-dark.qss

resources/styles/nheko.qss

resources/styles/system.qss

src/RoomList.cc

src/TextInputWidget.cc

src/TopRoomBar.cc