Use head elements and new manganis syntax in examples (#2688)

* use head elements and new manganis syntax in examples
* only enable desktop workspace example scraping during a dioxus release

---------

Co-authored-by: Jonathan Kelley <jkelleyrtp@gmail.com>

packages/fullstack/examples/hackernews/assets/hackernews.css

@@ -0,0 +1,17 @@
+@keyframes spin {
+    0% {
+        transform: rotate(0deg);
+    }
+
+    100% {
+        transform: rotate(360deg);
+    }
+}
+.spinner {
+    width: 10px;
+    height: 10px;
+    border: 4px solid #f3f3f3;
+    border-top: 4px solid #3498db;
+    border-radius: 50%;
+    animation: spin 2s linear infinite;
+}