pre {
  position: relative;  
}

.copy-code-button {
  position: absolute;
  top: 0.5em;
  right: 0.5em;
  padding: 0.5em 1em;
  font-size: 14px;
  background-color: #333;
  color: #fff;
  border: none;
  border-radius: 4px;
  cursor: pointer;
}