Fix /mirror subtab clicks (HTML-escaped < in highlightCode regex broke entire script) (#9)

- Mirror: unbreak subtab clicks (regex had HTML-escaped < in highlightCode) (c8408328010b9326e86c30c11371f33df908974a)

mirror.html

@@ -594,7 +594,7 @@ function highlightCode(code) {
     .replace(/\b(def|class|if|elif|else|for|while|return|import|from|as|with|try|except|raise|lambda|in|not|and|or|is|None|True|False)\b/g,
              '<span class="k">$1</span>')
     .replace(/(&quot;[^&]*?&quot;)/g, '<span class="s">$1</span>')
-    .replace(/(?&lt;![a-zA-Z_])(\d+)\b/g, '<span class="n">$1</span>');
+    .replace(/(?<![a-zA-Z_])(\d+)\b/g, '<span class="n">$1</span>');
 }
 
 function divergenceUpdate(userV, userA) {