[docs] add depends step to howto

Makefile

@@ -75,7 +75,7 @@ depends:
 	-@make depends$(UNAME)
 
 dependsLinux:
-	@sudo apt install golang pkg-config dh-golang golang-golang-x-text-dev cmake devscripts fakeroot debhelper curl g++ qt5-qmake qttools5-dev-tools qtdeclarative5-dev qml-module-qtquick-controls libqt5qml5 qtdeclarative5-dev qml-module-qt-labs-platform qml-module-qt-labs-qmlmodels qml-module-qtquick-extras qml-module-qtquick-dialogs
+	@sudo apt install golang pkg-config dh-golang golang-golang-x-text-dev cmake devscripts fakeroot debhelper curl g++ qt5-qmake qttools5-dev-tools qtdeclarative5-dev qml-module-qtquick-controls2 libqt5qml5 qtdeclarative5-dev qml-module-qt-labs-platform qml-module-qtquick-extras qml-module-qtquick-dialogs
 	@make -C docker deps
 	@# debian needs also: snap install snapcraft --classic; snap install  multipass --beta --classic
 

docs/test-float.rst

@@ -3,6 +3,7 @@ Testing float deployments
 You can quickly brand the client for test float instances.::
 
   export PROVIDER=floatdemo
+  make depends
   make vendor && make build
   build/qt/release/floatdemo-vpn