feat: add remark-smartypants for typographic improvements

app/posts/[slug]/page.tsx

@@ -3,9 +3,12 @@ import { MDXRemote } from 'next-mdx-remote/rsc'
 import { useMDXComponents } from '@/mdx-components'
 import remarkMath from 'remark-math'
 import remarkGfm from 'remark-gfm'
+import smartypants from 'remark-smartypants'
 import rehypePrettyCode from 'rehype-pretty-code'
+import rehypeAutolinkHeadings from 'rehype-autolink-headings'
 import rehypeKatex from 'rehype-katex'
 import rehypeSlug from 'rehype-slug'
+import rehypeExternalLinks from 'rehype-external-links'
 import { getPosts, getPost } from '@/lib/posts'
 import { TableOfContents } from '@/components/blog/TableOfContents'
 import { ScrollToTop } from '@/components/ui/ScrollToTop'
@@ -54,9 +57,10 @@ export default async function PostPage({ params }: { params: Promise<{ slug: str
                 components={useMDXComponents({})}
                 options={{
                   mdxOptions: {
-                    remarkPlugins: [remarkMath, remarkGfm],
-                    rehypePlugins: [
+                    remarkPlugins: [smartypants, remarkMath, remarkGfm],
+rehypePlugins: [
                       rehypeSlug,
+                      rehypeAutolinkHeadings,
                       [rehypePrettyCode, { theme: 'github-dark' }],
                       rehypeKatex,
                     ],