chore: mark main package side-effects free

Author: yyx990803

packages/vue/package.json

@@ -6,6 +6,7 @@
   "module": "dist/vue.runtime.esm-bundler.js",
   "types": "dist/vue.d.ts",
   "unpkg": "dist/vue.global.js",
+  "sideEffects": false,
   "files": [
     "index.js",
     "dist"