feat(css): Highlight non-existent pages with distinct styling

Added a new CSS class to highlight links to non-existent pages in red and appended a descriptive text indicator. This improves user navigation by clearly distinguishing between existing and non-existing pages, reducing confusion and enhancing the overall user experience.

src/wikimore/static/css/style.css

@@ -23,6 +23,15 @@ a:hover {
     text-decoration: underline;
 }
 
+a.new {
+    color: #ba0000;
+}
+
+a.new::after {
+    content: " (page does not exist)";
+    font-size: 0.8em;
+}
+
 /* Header styling */
 #header {
     background-color: #ffffff;