Pit in vue3.0 upgrade and correct posture for upgrade

1. The version of node should not be too low. The 11.x I used before was upgraded according to the official document

vue upgrade --next

Prompt me that the npm version is too low and needs to be upgraded

2. Install after upgrade

npm install -g @vue/cli

If the node version uses the latest version 16.3.0, an error will be reported.应该使用最新版稳定版14.17.1

correct upgrade posture

 1. nvm install 14.17.1
 2. nvm use 14.17.1
 3. npm install -g @vue/cli
 4. vue upgrade --next
 5. npm init @vitejs/app <你的项目文件夹 如果直接当前文件夹那么写`npm init @vitejs/app .`>
 6. npm install
 7. npm run dev

incomplete，，，