Update dependencies in package.json and package-lock.json; remove test posts and update welcome post with new content and formatting details.

src/app/api/posts/[slug]/route.ts

@@ -4,6 +4,10 @@ import path from 'path';
 import matter from 'gray-matter';
 import { remark } from 'remark';
 import html from 'remark-html';
+import gfm from 'remark-gfm';
+import remarkRehype from 'remark-rehype';
+import rehypeRaw from 'rehype-raw';
+import rehypeStringify from 'rehype-stringify';
 
 const postsDirectory = path.join(process.cwd(), 'posts');
 
@@ -21,7 +25,10 @@ async function getPostBySlug(slug: string) {
   const createdAt = getFileCreationDate(fullPath);
 
   const processedContent = await remark()
-    .use(html)
+    .use(gfm)
+    .use(remarkRehype, { allowDangerousHtml: true })
+    .use(rehypeRaw)
+    .use(rehypeStringify)
     .process(content);
 
   return {