app/styles/svg/loader.svg
<svg version="1.1" id="Layer_1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
width="50px" height="50px" viewBox="0 0 24 30" style="enable-background:new 0 0 50 50;" xml:space="preserve">
<rect x="0" y="0" width="4" height="20" fill="#333">
<animate attributeName="opacity" attributeType="XML"
values="1; .2; 1"
begin="0s" dur="0.6s" repeatCount="indefinite" />
</rect>
<rect x="7" y="0" width="4" height="20" fill="#333">
<animate attributeName="opacity" attributeType="XML"
values="1; .2; 1"
begin="0.2s" dur="0.6s" repeatCount="indefinite" />
</rect>
<rect x="14" y="0" width="4" height="20" fill="#333">
<animate attributeName="opacity" attributeType="XML"
values="1; .2; 1"
begin="0.4s" dur="0.6s" repeatCount="indefinite" />
</rect>
</svg>