Basic sticker pack editor

CMakeLists.txt

io.github.NhekoReborn.Nheko.yaml

resources/qml/Avatar.qml

resources/qml/RoomSettings.qml

resources/qml/ScrollHelper.qml

resources/qml/components/AvatarListTile.qml

resources/qml/dialogs/ImagePackEditorDialog.qml

resources/qml/dialogs/ImagePackSettingsDialog.qml

resources/res.qrc

src/Cache.cpp

src/Cache_p.h

src/MxcImageProvider.cpp

src/MxcImageProvider.h

src/SingleImagePackModel.cpp

src/SingleImagePackModel.h

src/timeline/TimelineModel.cpp

src/timeline/TimelineModel.h