ci: fix markdown formatting for contributing.md to pass markdownlint

fix markdown formatting for contributing.md to pass markdownlint

Signed-off-by: Rich Megginson <[email protected]>

Author: richm

contributing.md

@@ -74,6 +74,7 @@ To run the tests locally in container, you can use the attached Containerfile
 podman build -t system-roles-ssh .dev-tools
 podman run -itv ./:/src:Z system-roles-ssh
 ```
+
 ## Running CI Tests Locally
 
 ### Use tox-lsr with qemu