Custom 404 no longer shows

[andrewbridge]

Since 117180d, the custom 404 no longer renders on the site. I believe this is because we were dynamically rendering the 404 on every failure.

We don't want to dynamically render 404s as this is likely what has been eating up our Netlify invocations and rolling us into the paid for plan, but we'd also like to have an on-brand error page.

Unfortunately, there's nothing to directly pre-render a 404 page. To provide one to Netlify, you must create a 404.html in the site root. Currently, this ticket recommends moving your error handling to a component and then using this in both +error.svelte and a /404/+page.svelte so 404 route is creating during pre-render.