docs(theme-extension): add minimal TS example for theme.light and theme.dark overrides

Author: web-flow

docusaurus/docs/cms/admin-panel-customization/theme-extension.md

@@ -21,3 +21,25 @@ To extend the theme, use either:
 :::strapi Strapi Design System
 The default <ExternalLink to="https://github.com/strapi/design-system/tree/main/packages/design-system/src/themes" text="Strapi theme"/> defines various theme-related keys (shadows, colors…) that can be updated through the `config.theme.light` and `config.theme.dark` keys in `./admin/src/app.js`. The <ExternalLink to="https://design-system.strapi.io/" text="Strapi Design System"/> is fully customizable and has a dedicated <ExternalLink to="https://design-system-git-main-strapijs.vercel.app" text="StoryBook"/> documentation.
 :::
+
+### Example (TypeScript)
+
+```ts title="/src/admin/app.ts"
+export default {
+  config: {
+    theme: {
+      light: {
+        colors: {
+          primary600: '#4A6EFF',
+        },
+      },
+      dark: {
+        colors: {
+          primary600: '#9DB2FF',
+        },
+      },
+    },
+  },
+  bootstrap() {},
+}
+```