Add TOC and Layout components; update pages

src/components/ContentTOC.astro

@@ -0,0 +1,21 @@
+---
+import { getCollection } from "astro:content";
+
+const { sectionName } = Astro.props;
+
+const entries = (await getCollection(sectionName)).sort((a, b) =>
+  a.data.title.localeCompare(b.data.title),
+);
+
+const articles = entries.filter((entry) => entry.id !== "index");
+---
+
+<ul>
+    {articles.map((entry) => (
+        <li>
+            <a href={`/${sectionName}/${entry.id}`}>
+                {entry.data.title}
+            </a>
+        </li>
+    ))}
+</ul>