Add Vitest config for the skills app.

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/skills/vitest.config.ts

@@ -0,0 +1,8 @@
+import { defineConfig, mergeConfig } from "vitest/config";
+
+import sharedConfig from "../../vitest.shared";
+
+export default mergeConfig(
+  sharedConfig,
+  defineConfig({}),
+);