bootstrap dropdown ::after伪元素右对齐

<div class="dropdown">
  <button class="btn btn-primary dropdown-toggle" type="button" id="dropdownMenuButton" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
    Dropdown
  </button>
  <div class="dropdown-menu" aria-labelledby="dropdownMenuButton">
    <a class="dropdown-item" href="#">Action</a>
    <a class="dropdown-item" href="#">Another action</a>
    <a class="dropdown-item" href="#">Something else here</a>
  </div>
</div>

.dropdown-toggle::after {
  content: "";
  border-top: 0.3em solid;
  border-right: 0.3em solid transparent;
  border-left: 0.3em solid transparent;
  position: absolute;
  top: 50%;
  right: 1.5em;
  transform: translateY(-50%);
}