[release] 3.9.0

package.json

 {
   "name": "vue-element-admin",
-  "version": "3.8.1",
+  "version": "3.9.0",
   "description": "A magical vue admin. Typical templates for enterprise applications. Newest development stack of vue. Lots of awesome features",
   "author": "Pan <panfree23@gmail.com>",
   "license": "MIT",