Add link to git logo license (#199)

Author: mbtools

src/user-guide/other/logos.md

@@ -10,4 +10,6 @@ order: 65
 
 ![logo.png](/img/logo.png)
 
-![logo.svg](/img/logo.svg)
+![logo.svg](/img/logo.svg)
+
+[Git Logo](https://git-scm.com/downloads/logos) by [Jason Long](https://twitter.com/jasonlong) is licensed under the [Creative Commons Attribution 3.0 Unported License](https://creativecommons.org/licenses/by/3.0/).