This isn't a supported configuration but it should work, you just need to proxy from the web server to the internal IP of your Docker container - make sure ufw allows the connection.
If you're using Apache or commercial Litespeed you can do this with .htaccess. Something like:
RewriteEngine On
RewriteRule (.*) http://1.2.3.4/$1 [P]
Where 1.2.3.4 is the IP of your Docker container.
Obviously be careful which parts of the system you expose to the container, what capabilities you give it and which user you run the app under.
