Add custom 404

[IHIutch]

Adds a custom 404 page.

Cloudflare doesn't automatically show a 404 page like netlify, so this adds one.

[cloudflare-workers-and-pages]

Deploying maineballot with    Cloudflare Pages

Latest commit:	52a02e4
Status:	✅  Deploy successful!
Preview URL:	https://87e68df4.maineballot.pages.dev
Branch Preview URL:	https://add-404.maineballot.pages.dev

View logs

[IHIutch]

Looks like this isn't supported at the moment, with Astro's Cloudflare adapter. Tracking withastro/adapters#374

[IHIutch]

I was able to get the build working but I'm not sure this is better.

https://add-404.maineballot.pages.dev/404 works correctly, but only because that page is specifically defined like our other pages.

https://add-404.maineballot.pages.dev/four-oh-four renders the Astro 404 default page, but there's no way to get back to the original site. Which I don't think is a better experience than just seeing the homepage.