Run showdown output through sanitize

public/script.js

@@ -1225,6 +1225,9 @@ function messageFormatting(mes, ch_name, isSystem, isUser) {
          //console.log('mes after removed <tags>')
          //console.log(mes)
      } */
+
+    mes = DOMPurify.sanitize(mes);
+    
     return mes;
 }