By including the parserOptions as we do when we create an actual eslint config for normal projects, we get ESnext support for eslint during `vue serve`
BREAKING CHANGE: the "vueLoader" option has been removed. To modify vue-loader
options, use chainWebpack then `config.module.rule(vue).use(vue-loader).tap()`.
vue-loader has been upgraded to v15 and expects different options from v14.