Add a 404 page for sbt-typelevel-site

[armanbilge]

If we add it to the theme, users get it for free while still being able to override it themselves.

https://docs.github.com/en/pages/getting-started-with-github-pages/creating-a-custom-404-page-for-your-github-pages-site

[TonioGela]

What had you in mind? Adding a 404.html under src/main/resources/org/typelevel/sbt/site/helium and importing it here or merely adding a 404.md under docs?
If I'm not wrong the former won't add it for every plugin user, right?

[armanbilge]

If I'm not wrong the former won't add it for every plugin user, right?

That's exactly the point: to add a decent 404 page for every typelevel site out in the wild, at once.

[TonioGela]

If I'm not wrong the former won't add it for every plugin user, right?

That's exactly the point: to add a decent 404 page for every typelevel site out in the wild, at once.

But has that page to be built from scratch? Maybe I can try to make laika render a 404.md file into a 404.html and use this as a template, idk.

[armanbilge]

But has that page to be built from scratch?

Oh, I see. I'm not sure actually. You should check Laika docs, maybe we can have markdown templates.

Also note we can add a page completely programmatically. This example adds an HTML page, but it should work for markdown.

sbt-typelevel/site/src/main/scala/org/typelevel/sbt/site/TypelevelHeliumExtensions.scala

Lines 75 to 79 in abc217d

	.merge(
	apiUrl.fold(InputTree[F]) { url =>
	InputTree[F].addString(htmlForwarder(url), Path.Root / "api" / "index.html")
	}
	)

[abby-ql]

In #871 I injected the html in ThemeBuilder.addInputs similar to how the API forwarder page is added and still allowing users override the default by adding their own 404.md or 404.html. I did experiment with generating a default 404.md through mdoc so it would be fully rendered by Helium to make the style more aligned, but that ended up making the 404 page show up in navigation bar too, so I used the current approach instead. Would really appreciate feedback, thank you！