fix: add remark/rehype plugins for math and syntax highlighting in MDX pipeline

lib/posts.ts

@@ -4,6 +4,10 @@ import matter from 'gray-matter'
 import { compileMDX } from 'next-mdx-remote/rsc'
 import { cache } from 'react'
 import { useMDXComponents } from '@/mdx-components'
+import remarkMath from 'remark-math'
+import remarkGfm from 'remark-gfm'
+import rehypeKatex from 'rehype-katex'
+import rehypePrettyCode from 'rehype-pretty-code'
 
 const postsDirectory = path.join(process.cwd(), 'content/posts')
 
@@ -59,7 +63,16 @@ export const getPost = async (slug: string): Promise<Post | null> => {
   const { content: compiledContent } = await compileMDX({
     source: content,
     components,
-    options: { parseFrontmatter: true },
+    options: {
+      parseFrontmatter: true,
+      mdxOptions: {
+        remarkPlugins: [remarkMath, remarkGfm],
+        rehypePlugins: [
+          [rehypePrettyCode, { theme: 'github-dark' }],
+          rehypeKatex,
+        ],
+      },
+    },
   })
 
   return {