docs: add a link to next article (#1308)

docs/src/components/PageContent/PageContent.astro

@@ -1,9 +1,17 @@
 ---
-const {content, githubEditUrl} = Astro.props;
+const {content, githubEditUrl, currentPage} = Astro.props;
 const title = content.title;
 const headers = content.astro.headers;
 import MoreMenu from '../RightSidebar/MoreMenu.astro';
 import TableOfContents from '../RightSidebar/TableOfContents.tsx';
+import {getLanguageFromURL} from '../../util.ts';
+import {SIDEBAR} from '../../config.ts';
+const langCode = getLanguageFromURL(currentPage);
+const links = SIDEBAR[langCode].filter(x => x.link && typeof x.header === 'undefined');
+// handle cases with a trailing slash or not
+const index = links.findIndex(x => `/${x.link}/` === currentPage || `/${x.link}` === currentPage);
+const next = index !== -1 ? (index === links.length - 1 ? null : links[index + 1]) : null;
+const previous = index !== -1 ? (index === 0 ? null : links[index - 1]) : null;
 ---
 <style>
       .content {
@@ -38,4 +46,14 @@ import TableOfContents from '../RightSidebar/TableOfContents.tsx';
     <nav class="block sm:hidden">
         <MoreMenu editHref={githubEditUrl}/>
     </nav>
+    {
+      (previous || next) && <aside>
+      {
+        previous && <div>Previous Article: <a rel="prev" href={new URL(previous.link, Astro.site).pathname}>{previous.text}</a></div>
+      }
+      {
+        next && <div>Next Article: <a rel="next" href={new URL(next.link, Astro.site).pathname}>{next.text}</a></div>
+      }
+    </aside>
+    }
 </article>

docs/src/layouts/MainLayout.astro

@@ -111,7 +111,7 @@ const formatTitle = (content, SITE) => content.title ? `${content.title} 🚀 ${
         <LeftSidebar currentPage={currentPage} />
       </aside>
       <div id="grid-main">
-        <PageContent content={content} githubEditUrl={githubEditUrl}>
+        <PageContent content={content} githubEditUrl={githubEditUrl} currentPage={currentPage}>
           <slot />
         </PageContent>
       </div>