feat: add a QR-code page

[Tygo-van-den-Hurk]

Now you have to type out https://redirects.tygo.van.den.hurk.dev/<page> every time you'd like to sent someone somewhere. It'd be a great addition for mobile to add a /qr to end of the URL to be able to show a QR code to some one.

So you would go to https://redirects.tygo.van.den.hurk.dev/<page>/qr which would show you a QR code that goes to https://redirects.tygo.van.den.hurk.dev/<page>. That way it's super easy to share pages.

All you'd need to do is:

• define a template;
• work through the couple of pages that have been added already;
• and add it to all new pages.

and you're done. Best part? When you update a link the whole thing never breaks. As the QR-code points to the page, which is the thing that is being updated.