style: Modify anchor style.

Author: jaywcjlove

src/styles/markdown.less

@@ -596,7 +596,7 @@ body[data-color-mode*='light'] {
     color: var(--color-danger-fg);
   }
 
-  .anchor {
+  a.anchor {
     float: left;
     padding-right: 4px;
     margin-left: -20px;