Update single-source-of-truth.md: Add images

Author: aafulei

docs/single-source-of-truth.md

@@ -82,11 +82,18 @@ When users run
 today --help
 ```
 
-the program prints the embedded help message. The same help text, combined with
-the version output (`today --version`) is piped to the
-[`help2man`](https://www.gnu.org/software/help2man/) tool to automatically
-generate the man page. This generation is integrated into the Make build system
-and can be triggered with
+the program prints the embedded help message.
+
+![](./img/help.png)
+
+The same help text, combined with the version output (`today --version`) is
+piped to the[`help2man`](https://www.gnu.org/software/help2man/) tool to
+automatically generate the man page.
+
+![](./img/man.png)
+
+This generation is integrated into the Make build system and can be triggered
+with
 
 ```shell
 make man