App & Website under one Domain with Subfolders

Hey, following situation:

I am running my website on the root domain www.example.com - this website is hosted via webflow. Cloudflare DNS routes from www.example.com to the webflow site. Now I create a progressive webapp with ionic. The webapp is hosted on firebase and should be reached via the subfolder www.example.com/app/*

How do I setup such an architecture?