Lazy loading containers (#1411)

Co-authored-by: Asier Isayas <aisayas@microsoft.com>

less/resourceTree.less

@@ -11,6 +11,10 @@
   .collectionHeader {
     font-size: 12px;
   }
+
+  .loadMoreHeader {
+    color: RGB(5, 99, 193);
+  }
 }
 
 .notebookResourceTree {
@@ -23,6 +27,4 @@
   .clickDisabled {
     pointer-events: none;
   }
-}
-
-
+}