Added git ssh example to docs

Added a cli add git ssh dependency example to documentation for easy reference.

docs/docs/cli.md

@@ -200,6 +200,12 @@ You can also add `git` dependencies:
 poetry add git+https://github.com/sdispater/pendulum.git
 ```
 
+or use ssh instead of https:
+
+```bash
+poetry add git+ssh://git@github.com/sdispater/pendulum.git
+```
+
 If you need to checkout a specific branch, tag or revision,
 you can specify it when using `add`: