URL redirection is a webserver feature.
You'd have to configure your webserver to do the redirection.
Which webserver are you using?
If you'd enabled Pi-hole's web interface during installation, then that would be lighttpd, see Lighttpd pihole redirect for all other pages for a potential solution approach.
If you decided to use your own web server installation like nginx or apache, then that would have to be configured for your URL redirection.