chore: explicit build target version

Author: mascii

package.json

@@ -36,7 +36,7 @@
     "url": "https://github.com/mascii/vue-yup-form.git"
   },
   "scripts": {
-    "build": "tsup src/index.ts src/yup.ts --external './yup' --format cjs,esm --dts --clean",
+    "build": "tsup src/index.ts src/yup.ts --external './yup' --format cjs,esm --dts --target es2017 --clean",
     "format": "prettier ./{src,__tests__}/ --write",
     "test": "nr test:vue3 && nr test:vue2 && vue-demi-switch 3",
     "test:vue2": "vue-demi-switch 2.7 vue2 && vitest run --config ./config/vitest.ts --coverage",