Update Git.md

Author: Snailclimb

docs/tools/Git.md

@@ -256,3 +256,4 @@ git push origin
 - [图解Git](http://marklodato.github.io/visual-git-guide/index-zh-cn.html)
 - [猴子都能懂得Git入门](https://backlog.com/git-tutorial/cn/intro/intro1_1.html)
 - https://git-scm.com/book/en/v2
+- [Generating a new SSH key and adding it to the ssh-agent](https://help.github.com/en/articles/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent)