install @buuug7/simplify-button package via npm, and then import from @buuug7/simplify-button/index.css file.
npm install @buuug7/simplify-button
default
<button class="btn">BUTTON</button>small
<button class="btn small">SMALL</button>primary
<button class="btn primary">BUTTON</button>outline
<button class="btn outline">BUTTON</button>link
<button class="btn link">BUTTON</button>block
<button class="btn block">BUTTON</button>