FIX: Lab image should load "eager" (jupyter#555)

Author: palewire

index.html

@@ -292,7 +292,7 @@ <h4 class="jumbotron-text">{{ page.jumbotron.text }}</h4>
                                  height={{ page.jupyterlab.image.height }}
                                  class="img-responsive"
                                  id="portal"
-                                 loading="lazy" />
+                                 loading="eager" />
                         </picture>
                     </div>
                     <div class="col-md-6 nb-highlight-text">