README: Add missing "git add"

The command "git add" was missing in the instructions for creating the
commit. Add the command for correct instructions.

Signed-off-by: Razvan Deaconescu <razvan@rosedu.org>

Author: razvand

README.md

@@ -139,6 +139,7 @@ We do the steps:
 1. Create commit:
 
    ```console
+   git add c-bye/
    git commit -s -m 'Introduce c-bye program'
    ```