Add dark mode to body for single story

Author: mayan-000

.storybook/preview-styles.css

@@ -18,4 +18,8 @@
  #storybook-docs .sbdocs-content h2 {
    font-weight: 800;
    font-size: 24px;
- }
+ }
+
+ .dark body {
+	 background-color: #171717 !important;
+ }