README.md: add an example

Signed-off-by: Trevor Gamblin <[email protected]>

Author: threexc

README.md

@@ -37,6 +37,17 @@ Then install with pip:
 pip install .
 ```
 
+## Examples
+
+Test a patch (the sample file is generated using `git format-patch` on commit d7de60340ec9 in this repository):
+
+```console
+(venv) tgamblin@workbox:~/git/patchtest2$ patchtest --patch 0001-README.md-update-Installation-instructions.patch
+PASS: test_mbox_signed_off_by_presence on [PATCH] README.md: update Installation instructions
+PASS: test_mbox_shortlog_format on [PATCH] README.md: update Installation instructions
+FAIL: test_mbox_commit_message_presence on [PATCH] README.md: update Installation instructions (Please include a commit message on your patch explaining the change)
+```
+
 ## License
 
 `patchtest2` is distributed under the terms of the [MIT](https://spdx.org/licenses/MIT.html) license.