fix bug

js/customElements/blogIndex.js

@@ -16,7 +16,7 @@ class BlogIndex extends HTMLElement {
                         article.appendChild(h2);
 
                         const content = document.createElement("p");
-                        content.classList.appendChild("breakWord");
+                        content.classList.add("breakWord");
                         content.innerHTML = element["content"];
                         article.appendChild(content);