Update email signature link to use absolute path

Author: YoshiroMaximus

tools.html

@@ -299,7 +299,7 @@ <h1>Tools</h1>
           </div>
         </a>
 
-        <a class="tool-card" href="email-signature.html">
+        <a class="tool-card" href="/tools/email-signature.html">
           <div class="tool-header">
             <span class="tool-name">GWHS Email Signature</span>
             <span class="tool-type">utility</span>