webpack 5

Hello easy-team,

I really like your tools!

I tried upgrading this example to webpack 5 by upgrading the following dependencies:

```json
"easywebpack-cli": "^5.0.0"
"easywebpack-vue": "^5.0.1"
"egg-webpack": "^5.0.1"
```

However it does not work ... the generated browser code is not executable.

Could you give it a try?

Miguel
