Update package.json

update version for release-2.21.0

package.json

@@ -1,6 +1,6 @@
 {
   "name": "temporay-parking",
-  "version": "2.20.0",
+  "version": "2.21.0",
   "private": true,
   "scripts": {
     "serve": "cross-env NODE_ENV=dev vue-cli-service serve",