Render embedded code preview by permlink in markdown (#30234)

The permlink in markdown will be rendered as a code preview block, like GitHub

Co-authored-by: silverwind <me@silverwind.io>

web_src/css/base.css

@@ -1186,10 +1186,13 @@ overflow-menu .ui.label {
   content: attr(data-line-number);
   line-height: 20px !important;
   padding: 0 10px;
-  cursor: pointer;
   display: block;
 }
 
+.code-view .lines-num span::after {
+  cursor: pointer;
+}
+
 .lines-type-marker {
   vertical-align: top;
 }