Add ci check to validate tsdown output

Author: samchungy

.github/workflows/test.yml

@@ -39,3 +39,6 @@ jobs:
 
       - name: Build
         run: pnpm build
+
+      - name: Validate package
+        run: pnpm validate:pack

package.json

@@ -51,7 +51,8 @@
     "release": "pnpm build && changeset publish",
     "test": "vitest run",
     "test:ci": "vitest run --coverage",
-    "test:watch": "vitest"
+    "test:watch": "vitest",
+    "validate:pack": "attw --pack ."
   },
   "devDependencies": {
     "@arethetypeswrong/cli": "0.18.2",