Refactor error handling in HTMLLoader, enhance error templates, and add new entry and setup templates

public/templates/error/error.css

@@ -1,3 +1,18 @@
 .icon {
+    display: flex;
+    justify-content: center;
+    align-items: center;
     font-size: 100pt;
+}
+
+.text {
+    text-align: center;
+    font-family: Verdana, Geneva, Tahoma, sans-serif;
+}
+
+.code {
+    font-family: monospace;
+    background-color: rgb(226, 225, 225);
+    padding: 1px;
+    border-radius: 5px;
 }

public/templates/error/error.html

@@ -11,6 +11,10 @@
         <div class="icon">
             ⚠️
         </div>
+        <div class="text">
+            <h2>Error</h2>
+            <p>%error%</p>
+        </div>
     </div>
 </body>
 </html>