[pkg] add float-deployed demo libpvn for tests

branding/assets/demolib

branding/config/demolib-ca.crt

branding/config/vendor.conf

gui/backend.go

gui/handlers.cpp

gui/handlers.h

gui/qml/LoginDialog.qml

gui/qml/main.qml

pkg/backend/api.go

pkg/backend/status.go

pkg/config/config.go