Как добавить свою svg стрелку в select

*,
*:before,
*:after {
  box-sizing: border-box;
}

* {
  padding: 0;
  margin: 0;
}

body {
  padding: 4em;
}

.select {
  height: 40px;
  width: 100%;
  overflow: hidden;
  position: relative;
  border-radius: 3px;
  margin-bottom: 1em;
}

.select:after {
  content: "▼";
  padding: 12px 8px;
  position: absolute;
  right: 0px;
  top: 0;
  z-index: 1;
  text-align: center;
  width: 10%;
  height: 100%;
  pointer-events: none;
}

.select__field {
  height: 40px;
  width: 100%;
  padding: 5px 15px;
  color: #616263;
  background-color: #ececec;
  border: 1px solid #e3e3e3;
  outline: none;
  font-size: 16px;
  -webkit-appearance: none;
  -moz-appearance: none;
  appearance: none;
}

.select__field::-ms-expand {
  display: none;
}

.select__field:focus:invalid {
  border-color: #FD6347;
}

.select__field:required:valid {
  border-color: #006400;
}

<div class="select">
  <select name="nameValueSelect" class="select__field" name="pets" id="pet-select">
    <option value="">--Please choose an option--</option>
    <option value="dog">Dog</option>
    <option value="goldfish">Goldfish</option>
  </select>
</div>

select{
  -moz-appearance:none; /* Firefox */
  -webkit-appearance:none; /* Safari and Chrome */
  appearance:none;
  background-image: url("https://cdn-icons-png.flaticon.com/512/6879/6879387.png");
  background-size: contain;
  background-repeat: no-repeat;
  background-position: right;
  padding: 6px 24px 6px 0;
}

<label for="pet-select">Choose a pet:</label>
<select name="pets" id="pet-select">
    <option value="">--Please choose an option--</option>
    <option value="dog">Dog</option>
    <option value="goldfish">Goldfish</option>
</select>