Bootstrap 4 Carousel显示上一张和下一张图片并在中间显示

Question

如何在bootsrap 4 carasoul中预览next和prev滑块图像 我无法自定义它，我曾试过光滑的滑块，但响应行为并不是那么好

<link href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-PsH8R72JQ3SOdhVi3uxftmaW6Vc51MKb0q5P2rRUpPvrszuE4W1povHYgTpBfshb" crossorigin="anonymous">
<div id="carouselExampleIndicators" class="carousel slide" data-ride="carousel">
  <ol class="carousel-indicators">
    <li data-target="#carouselExampleIndicators" data-slide-to="0" class="active"></li>
    <li data-target="#carouselExampleIndicators" data-slide-to="1"></li>
    <li data-target="#carouselExampleIndicators" data-slide-to="2"></li>
  </ol>
  <div class="carousel-inner" role="listbox">
    <div class="carousel-item active">
      <img class="d-block img-fluid" src="..." alt="First slide">
    </div>
    <div class="carousel-item">
      <img class="d-block img-fluid" src="..." alt="Second slide">
    </div>
    <div class="carousel-item">
      <img class="d-block img-fluid" src="..." alt="Third slide">
    </div>
  </div>
  <a class="carousel-control-prev" href="#carouselExampleIndicators" role="button" data-slide="prev">
    <span class="carousel-control-prev-icon" aria-hidden="true"></span>
    <span class="sr-only">Previous</span>
  </a>
  <a class="carousel-control-next" href="#carouselExampleIndicators" role="button" data-slide="next">
    <span class="carousel-control-next-icon" aria-hidden="true"></span>
    <span class="sr-only">Next</span>
  </a>
</div>

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js" ></script>




<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/js/bootstrap.min.js" integrity="sha384-alpBpkh1PFOepccYVYDB4do5UnbKysX5WZXm3XxPqe5iKTfUKjNkCk9SaVuEZflJ" crossorigin="anonymous"></script>

<script src="https://gist.githubusercontent.com/FezVrasta/16c5d5e5ff1211922ddcf090c8454d74/raw/9372bdf66f7d899a5daaf0ff06ff89be92561c83/popper.min.js" ></script>

无法插入popper.js我不知道为什么请帮助和谢谢