Edit in JSFiddle

<p>This is a sentence that contains an <a href="#" class="external">external link<span> (opens in new window)</span></a> which you can see from this icon. Furthermore, there is a note for screen readers.</p>
.external::after {
  content: "";
  display: inline-block;
  width: 0.75em;
  height: 0.75em;
  background-image: url("https://static.oswaldlabs.com/e80rj23-external.svg");
  background-size: contain;
  background-repeat: no-repeat;
  vertical-align: middle;
  margin-left: 0.25em;
  margin-right: 0.1em;

.external span:last-child {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;

These are general styles, unrelated to this example

body {
  background: #fff;
  color: #001b01;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji";
  line-height: 1.6;