Add elastic (#521)

* add elastic-vertical-reverse.svg

* add elastic.svg

* Update README.md

* Update index.md

Co-authored-by: Terence Eden <edent@users.noreply.github.com>

images/svg/elastic.svg

@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg"
+aria-label="elastic" role="img"
+viewBox="0 0 512 512"><rect
+width="512" height="512"
+rx="15%"
+fill="#fff"/><path d="m206.4 217.2 90.1 40.3 90.9-78.1A101.6 99.7 0 0 0 203.9 103.4l-15.1 76.9z" fill="#ffd00a"/><path d="m113.1 310.8a103.4 101.4 0 0 0-2 19.9 101.9 99.9 0 0 0 186.1 56.2l15-76.7-20-37.5-90.5-40.4z" fill="#20b9af"/><path d="m112.6 157.9 61.7 14.3 13.5-68.9a48.8 47.8 0 0 0-75.2 54.6" fill="#ee5096"/><path d="m107.2 172.3a68.1 66.8 0 0 0-3 125.8l86.6-76.8-15.9-33.3z" fill="#12a5df"/><path d="m313.1 386.9a48.7 47.8 0 0 0 75.1-54.5l-61.7-14.2z" fill="#90c640"/><path d="m325.6 302.4 67.9 15.6a68.7 67.4 0 0 0 46.8-63.4 68 66.7 0 0 0-43.9-62.3l-88.8 76.4z" fill="#05799f"/></svg>