404 page

works (almost) the same as with hugo

TODO: create 404.html rather than 404/index.html?

Your 404.html file can be set to load automatically when a visitor enters a mistaken URL path, dependent upon the web serving environment you are using. For example:

GitHub Pages and GitLab Pages. The 404 page is automatic.
Apache. You can specify ErrorDocument 404 /404.html in an .htaccess file in the root of your site.
Nginx. You might specify error_page 404 /404.html; in your nginx.conf file. Details here.
Amazon AWS S3. When setting a bucket up for static web serving, you can specify the error file from within the S3 GUI.
Amazon CloudFront. You can specify the page in the Error Pages section in the CloudFront Console. Details here
Caddy Server. Using errors { 404 /404.html }. Details here
Netlify. Add /* /404.html 404 to content/_redirects. Details Here
Azure Static website. You can specify the Error document path in the Static website configuration page of the Azure portal. More details are available in the Static website documentation.