Make Nheko compile on Qt6

CMakeLists.txt

src/Cache.cpp

src/ChatPage.cpp

src/CompletionProxyModel.cpp

src/GridImagePackModel.cpp

src/InviteesModel.h

src/JdenticonProvider.h

src/LoginPage.cpp

src/MainWindow.cpp

src/MatrixClient.cpp

src/MxcImageProvider.cpp

src/MxcImageProvider.h

src/SingleImagePackModel.cpp

src/UserSettingsPage.cpp

src/Utils.cpp

src/dbus/NhekoDBusApi.h

src/emoji/Provider.h

src/main.cpp

src/timeline/CommunitiesModel.cpp

src/timeline/DelegateChooser.cpp