How to have Single App mode for a web app on an iPad using Apple Configurator 2?
Yes that is possible and it is even easier then using Apple Configurator 2. You just need to go to settings-> general->accessibility->Guided Access.

Then when you are in the webapp click three times the home button and draw where the you user can not interact anymore. They can not leave the app, or use the home and power button.

I hope this is what you are looking for.