feat: custom lang highlight, images dir, width bump, first post

- Wire up Ergon and ArchASM custom highlight.js languages
- Serve /content/images/ for post image embeds
- Blog width 820px -> 1040px to match landing page
- First real blog post: "Why make a blog?"

👾 Generated with [Letta Code](https://letta.com)

Co-Authored-By: Letta Code <noreply@letta.com>

main.go

@@ -16,6 +16,7 @@ func main() {
 		http.ServeFile(w, r, "ABSTRACTS.png")
 	})
 	mux.Handle("/src/", http.StripPrefix("/src/", http.FileServer(http.Dir("src"))))
+	mux.Handle("/content/images/", http.StripPrefix("/content/images/", http.FileServer(http.Dir("content/images"))))
 
 	if err := blog.RegisterRoutes(mux, "content/posts"); err != nil {
 		log.Fatalf("blog: %v", err)