How to force sveltekit app to redirect to HTTPS on Heroku

I have a domain on Namecheap that points to my Heroku instance via an ALIAS.

ALIAS @ example.com

I have the automatic SSL certificate enabled on my Heroku instance.

Accessing http://example.com and https://example.com works.

However, I want to disallow HTTP navigation by enforcing HTTPS.

According to Heroku, that must be handle at application level.

How can I do this with SvelteKit?