Add Bootstrap CSS to Vuepress

yarn add bootstrap # or npm install bootstrap --save

// import 'bootstrap/scss/bootstrap.scss';import 'bootstrap/dist/css/bootstrap.css';export default ({  Vue, // the version of Vue being used in the VuePress app  options, // the options for the root Vue instance  router, // the router instance for the app  siteData // site metadata}) => {}

---title: Test---<button class="btn btn-primary">Click Me</button>