Merge pull request #228 from 10gen/card-icons

Updating card icons for Dark Mode

Author: mayaraman19

source/images/chapter-icon-atlas.png

@@ -34,7 +34,7 @@ Start with Guides
          Learn how to create a cluster, load a sample dataset, and
          get your connection information.
       :image: /images/chapter-image-atlas.png
-      :icon: /images/chapter-icon-atlas.png
+      :icon: atlas_database
 
       .. guide:: /atlas/account.txt
       .. guide:: /atlas/cluster.txt
@@ -47,7 +47,7 @@ Start with Guides
       :description: Learn how to perform these core operations with
          your preferred language and associated MongoDB Driver.
       :image: /images/chapter-image-crud.png
-      :icon: /images/chapter-icon-crud.png
+      :icon: general_action_read
 
       .. guide:: /crud/install.txt
       .. guide:: /crud/read.txt