Add note on preserveAspectRatio for SVG

Author: josephrexme

animations/svg.md

@@ -22,3 +22,11 @@ Morphing is changing the coordinate values of a paths. Here are some examples:
 - Svg provides fallback for non supporting browsers with `switch` and `foreignObject`. [This tweet by Sara Soueidan for more](https://twitter.com/SaraSoueidan/status/875112721922043904)
 - Export SVG to Gif with Chris Gannon's tool [here](https://github.com/chrisgannon/SVG2GIF)
 
+
+## Snippets
+Using preserveAspectRatio:
+```
+preserveAspectRatio="xMidYMid meet" => background-size: contain
+preserveAspectRatio="xMidYMid slice" => background-size: cover
+```
+