Some qt6 prep

.gitignore

src/BlurhashProvider.h

src/Cache.cpp

src/ChatPage.cpp

src/CompletionProxyModel.cpp

src/JdenticonProvider.h

src/LoginPage.cpp

src/MatrixClient.cpp

src/MxcImageProvider.cpp

src/MxcImageProvider.h

src/RegisterPage.cpp

src/TrayIcon.cpp

src/TrayIcon.h

src/UserSettingsPage.cpp

src/Utils.cpp

src/WelcomePage.cpp

src/dialogs/CreateRoom.cpp

src/dialogs/FallbackAuth.cpp

src/dialogs/ImageOverlay.cpp

src/dialogs/Logout.cpp