Fix: Restore custom 404 page

GitHub Pages requires the page to be located in the root of the content directory and named 404.html

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

- - - - - - - - - - - - - - - - - - - -

Close #988

Author: antross

docs/404/index.html docs/404.html

@@ -254,17 +254,6 @@ gulp.task('move:images', moveImages);
 gulp.task('move:scanimages', moveScanImages);
 gulp.task('optimize:images', gulp.series('move:docimage', 'imagemin', 'move:images', 'move:scanimages'));
 
-gulp.task('404', (done) => {
-    const lostContent = fs.readFileSync(`${dirs.dist}/404/index.html`, 'utf-8'); // eslint-disable-line no-sync
-    const asp404 = `<%@ EnableSessionState=False %>
-<% Response.Status = "404" %>
-${lostContent}`;
-
-    fs.writeFileSync(`${dirs.dist}/404/index.asp`, asp404, 'utf-8'); // eslint-disable-line no-sync
-
-    done();
-});
-
 // ---------------------------------------------------------------------
 // | Main tasks                                                        |
 // ---------------------------------------------------------------------
@@ -359,7 +348,6 @@ gulp.task('build', gulp.series(
     // TODO: Re-enable pre-compression once supported by GitHub Pages
     //'compress:zopfli',
     //'compress:brotli',
-    '404'
 ));
 
 gulp.task('default', gulp.series('build'));

docs/404/index.asp

@@ -2,7 +2,7 @@
 section: "placeholder-pages"
 layout: "error"
 originalFile: "404.md"
-permalink: "404/index.html"
+permalink: "404.html"
 title: "Oh oh"
 contentType: "details"
 sitemap: "false"