fix 26348: add container diff --latest doc

Signed-off-by: Marek Libra <marek.libra@gmail.com>

docs/source/markdown/podman-container-diff.1.md.in

@@ -44,6 +44,11 @@ $ podman container diff --format json container1 container2
 }
 ```
 
+```
+$ podman container diff --latest
+C /etc
+```
+
 ## SEE ALSO
 **[podman(1)](podman.1.md)**, **[podman-container(1)](podman-container.1.md)**