Add theme property to Icon schema (#1290)

Co-authored-by: Konstantin Konstantinov <KKonstantinov@users.noreply.github.com>

Author: DaleSeo

src/types.ts

@@ -279,7 +279,15 @@ export const IconSchema = z.object({
      *
      * If not provided, the client should assume that the icon can be used at any size.
      */
-    sizes: z.array(z.string()).optional()
+    sizes: z.array(z.string()).optional(),
+    /**
+     * Optional specifier for the theme this icon is designed for. `light` indicates
+     * the icon is designed to be used with a light background, and `dark` indicates
+     * the icon is designed to be used with a dark background.
+     *
+     * If not provided, the client should assume the icon can be used with any theme.
+     */
+    theme: z.enum(['light', 'dark']).optional()
 });
 
 /**