fix(Storybook-Darkmode): fixed background-flashing in darkmode (#1928)

- changed background-color of flashing-elements to transperent
- remove placeholder

packages/storybook-utils/src/index.css

@@ -24,3 +24,14 @@
  /* same as Storybook color "textMuted" inside ./theme.ts */
  color: var(--onyx-color-text-icons-neutral-medium);
 }
+
+/* To prevent bg flashing when changing between elements in darkmode */
+.sb-preparing-story,
+.sb-preparing-docs {
+ background-color: transparent;
+}
+/* removed placeholder for the same reason */
+.sb-previewBlock,
+.sb-argstableBlock {
+ display: none;
+}