replace extract-text-webpack-plugin (deprecated) by mini-css-extract-plugin. Try to make webpack-dev-server work again on the project
<div class="modal-mask diff-panel" v-show="display">
<p class="pull-right close-btn" @click="close"> <i class="fa fa-close"></i> </p>
<slot name="header"></slot>
<slot name="content"></slot>
<slot name="footer"></slot>
</div>