fix: apply monospace for codes

assets/css/style.scss

@@ -10,10 +10,14 @@ footer p:last-child::before {
     content: none;
 }
 
-*, h1 {
+body, h1 {
     font-family: Pretendard;
 }
 
+div.highlight {
+    font-family: monospace!important;
+}
+
 .post-content {
     font-size: 110%;
 }