Able to export page to file instead of directory that can support github page 404

[nghenglim]

Is your feature request related to a problem? Please describe.
Currently I rewrite my blog with sapper, and host it with github page. however there is a problem that github page require 404.html and not 404/index.html

Describe the solution you'd like
when run sapper export, provide a way to export svelte page in file whenever possible

Describe alternatives you've considered
currently I manually copy paste 404/index.html to 404.html, however I believe due to this reason, some feature like routing will be broken (therefore I make a redirection on this page >.<).

How important is this feature to you?
Mainly I need this feature to perform redirection based on the blogpost slug, example , currently due to the custom way I do it, seems like it is buggy intermittently

Additional context
seems like code inside the <script></script> tag in 404.svelte is not working too in route that redirected to github 404.html , I need to add custom script below template.html to simulate a script behavior in 404.svelte, which is not ideal

[chuvikovd]

Maybe it is possible to add extra step to export crawling process, where script opens /404 page and saves it to export folder root? This way we can ensure that _error.svelte default is used when 404.svelte not exist.

[swyxio]

i think this can be automated with a bash script, unless the sapper maintainers want to explicitly support a github build target.

[Conduitry]

Fixed in 0.27.13 via #1049.